RBSE Solutions Class 8 Science Chapter 14 Refraction of Light

Refraction Of Light Textbook Questions Solved

I. Multiple Choice Questions

Question 1. 1. Which of the following event is not related to refraction of light?
(a) The bottom of water filled bowl appears raised.
(b) Appearance of sun before sun rising and after sunset
(c) Formation of image by mirror
(d) Twinkling of stars
2. Which is not a part of a human eye?
(a) Retina
(b) Cornea
(c) Pupil
(d) Mid plane
3. When a ray of light enters into rarer medium from denser medium, it bends
(a) Away from normal
(b) Towards to normal
(c) Move in straight line without deviation.
(d) None of the options
Answer:
1. (c) Formation of image by mirror
2. (d) Mid plane
3. (a) Away from normal
In simple words: Refraction is when light bends as it passes from one material to another. Making an image with a mirror does not involve light bending as it changes material, so it is not refraction. The mid plane is not part of the eye, while the retina, cornea, and pupil are all key parts. When light moves from a denser material to a rarer one, it speeds up and bends away from the imaginary line called the normal.

🎯 Exam Tip: For multiple-choice questions, eliminate obviously incorrect options first. Remember that mirrors work by reflection, not refraction, and understand the basic parts of the eye and how light behaves when changing mediums.

Question 2. Fill in the blanks
1. Iris of eye controls the amount of light entering into eye.
2. The image formation by a convex lens is always erect, virtual and small.
3. Light ray enters into water medium from air bends towards the normal.
Answer:
1. Iris
2. Convex lens
3. towards
In simple words: The iris controls how much light enters the eye. A convex lens can form images that are upright, not real, and small. When light moves from air into water, it bends towards the normal line.

🎯 Exam Tip: Remember the basic functions of eye parts and the rules of light refraction, especially how light bends when moving between different mediums. For fill-in-the-blanks, think about the key terms related to the topic.

Question 3. Match Column A with column B

Answer:
1. (d) Eye fluid.
2. (a) Vitreous Humour
3. (b) Iris
4. (a) Vitreous Humour
In simple words: The fluid between the lens and cornea is called aqueous humour, which is a type of eye fluid. The clear, jelly-like substance between the lens and retina is called vitreous humour. The iris is the dark, muscular part located behind the cornea. According to the provided answer, the area where the image is formed is also matched to vitreous humour.

🎯 Exam Tip: Familiarize yourself with the various parts of the human eye and their specific functions, particularly the different fluids and structures involved in vision.

Refraction Of Light Short Answer Type Questions

Question 1. What is refraction? What is the cause of refraction?
Answer: When a light ray moves from one medium into another, it changes its path and bends. This bending of light is called refraction. The main reason for refraction is that the speed of light changes as it travels through different mediums. For example, light moves slower in a denser medium like glass compared to a rarer medium like air. This change in speed causes the light to bend at the boundary between the two mediums. This difference in speed is why refraction happens when light goes from one medium to another.
In simple words: Refraction is when light bends as it passes from one material to another. This happens because light travels at different speeds in different materials.

🎯 Exam Tip: Clearly define refraction and then explain its cause by focusing on the change in the speed of light. Using simple analogies can help in understanding this concept.

Question 3. Define the refraction coefficient.
Answer: Refraction coefficient, also known as refractive index \((\mu)\), is the ratio of the speed of light in the first medium to the speed of light in the second medium. It is a constant value for any two given mediums and does not have any units.
\( \text{Refraction coefficient } (\mu) = \frac { \text{Speed of light in first medium} }{ \text{Speed of light in second medium} } \)
\( \implies \mu = \frac { V_1 }{ V_2 } \)
In simple words: The refraction coefficient tells us how much light slows down or speeds up when it goes from one material to another. It is found by dividing the speed of light in the first material by its speed in the second material.

🎯 Exam Tip: When defining refractive index, always include both the word definition (ratio of speeds) and the mathematical formula. Emphasize that it is a dimensionless quantity.

Question 4. What do you mean by dispersion? Write the sequence of colours in rainbow.
Answer: Dispersion of light is the phenomenon where white light splits into its seven constituent colours when it passes through a transparent medium like a prism. This happens because each colour of light travels at a slightly different speed through the medium, causing them to bend at different angles. When white light enters a prism, it separates into a band of seven colours: Violet, Indigo, Blue, Green, Yellow, Orange, and Red. This sequence of colours is also seen in a rainbow, which is caused by the dispersion of sunlight through raindrops.
In simple words: Dispersion is when white light breaks up into all its different colours, like in a rainbow. This happens because each colour bends differently when it passes through something like water or a glass prism. The order of colours is VIBGYOR.

🎯 Exam Tip: Clearly define dispersion and then accurately list the order of colours in a spectrum (VIBGYOR). Mentioning a prism or rainbow helps illustrate the concept.

Question 5. The two classmates of Meena are Raghav and Megha, Raghav is not able to see distant objects and Megha is not able to see near objects. What are eye's defects they have? To remove these defects which type of lens they should use in their spectacles?
Answer: Raghav cannot see distant objects clearly, which means he has shortsightedness, also known as myopia. This defect is corrected by using a concave lens in his spectacles. Megha cannot see near objects clearly, which means she has longsightedness, also known as hypermetropia. This defect is corrected by using a convex lens in her spectacles. Using the correct lens type helps focus light properly on the retina, allowing for clear vision.
In simple words: Raghav has myopia (can't see far), so he needs concave lenses. Megha has hypermetropia (can't see near), so she needs convex lenses.

🎯 Exam Tip: Remember the two main vision defects: myopia (shortsightedness) and hypermetropia (longsightedness), and the specific type of lens (concave or convex) used to correct each.

Refraction Of Light Long Answer Type Questions

Question 1. Explain the refraction of light rays from glass slab with a pictorial diagram.
Answer: When a ray of light passes through a rectangular glass slab, it undergoes refraction twice. First, when it enters from a rarer medium (air) to a denser medium (glass), and second, when it exits from the denser medium (glass) back into the rarer medium (air). When light enters the glass slab from the air, it bends towards the normal. As it travels through the glass and then exits back into the air, it bends away from the normal. The emergent ray is parallel to the incident ray but is slightly displaced laterally. This displacement shows that the light ray has deviated from its original path without changing its direction.

In simple words: When light shines through a flat piece of glass, it bends twice. First, when it enters from the air into the glass, it bends a little. Then, when it leaves the glass and goes back into the air, it bends again. The light comes out going in the same direction as it started, but it has shifted slightly to the side.

🎯 Exam Tip: When drawing the ray diagram for a glass slab, ensure that the emergent ray is parallel to the incident ray, and clearly show the bending of light towards the normal when entering a denser medium and away from it when entering a rarer medium.

Question 2. Name the optical instruments which use lens. Describe it in brief.
Answer: Lenses are used in many optical instruments that help us see better or observe tiny objects. Common examples include spectacles, simple microscopes, and compound microscopes. Spectacles use either convex or concave lenses to correct vision defects like shortsightedness (myopia) and longsightedness (hypermetropia), ensuring light focuses correctly on the retina. A simple microscope typically uses a single convex lens with a short focal length to magnify small objects, often used by watch repairers. A compound microscope uses two convex lenses, an objective lens, and an eyepiece, fitted in a tube to provide much higher magnification, allowing us to see very small details of objects.
In simple words: Lenses are found in things like eyeglasses (spectacles), magnifying glasses (simple microscopes), and powerful microscopes (compound microscopes). Eyeglasses fix blurry vision, simple microscopes make small things look bigger, and compound microscopes make tiny things look much, much larger.

🎯 Exam Tip: For each instrument, identify the type of lens used and its primary function. For microscopes, specify if it uses one or more lenses and what kind of magnification it provides.

Question. Explain in brief the working and structure by human eye.
Answer: The human eye is a complex organ that works like a camera to let us see. It has a convex lens made of flexible muscles. Light enters the eye through the transparent cornea at the front. Behind the cornea is the iris, a dark, muscular structure that controls the size of the pupil, a small hole in its center. The pupil adjusts to allow more light in dim conditions and less in bright conditions. The eye lens focuses light onto the retina at the back of the eye. The retina is a light-sensitive membrane with many nerves that send signals to the brain. Although the image formed on the retina is inverted, the brain processes these signals to perceive the image as upright and clear. The space between the cornea and lens is filled with aqueous humor (eye fluid), and the space between the lens and retina is filled with vitreous humor.

In simple words: The eye works like a camera. Light goes through the cornea and pupil (which changes size), then through the eye lens. This lens focuses the light onto the retina at the back. The retina sends signals to the brain, which turns the upside-down image into what we actually see. Different fluids fill the eye to keep its shape and help light pass through.

🎯 Exam Tip: When describing the eye, mention the key parts (cornea, pupil, iris, lens, retina, optic nerve) and their role in light entry, focusing, and image formation. A simple diagram can greatly enhance your explanation.

Refraction Of Light Additional Questions Solved

I. Multiple Choice Questions

Question 1. The process of bending light into seven colours is called
(a) Deflection
(b) Dispersion
(c) Spectrum
(d) Normal
Answer: (b) Dispersion
In simple words: When white light separates into its full range of colours, like a rainbow, that process is called dispersion.

🎯 Exam Tip: Remember that dispersion specifically refers to the splitting of white light into its constituent colours, as opposed to simply bending (refraction) or bouncing (reflection).

Question 3. In cataract, the lens of the eye becomes
(a) Clear
(b) small
(c) Large
(d) opaque
Answer: (d) opaque
In simple words: Cataract is an eye condition where the clear lens of the eye becomes cloudy or opaque, making it hard to see clearly.

🎯 Exam Tip: Associate cataract with the clouding or opacification of the eye's lens, which impairs vision and is treatable by surgery.

Question 4. At what position of the object does a convex lens act as a magnifying glass?
(a) between F and 2F
(b) between F and O
(c) Beyond F
(d) Beyond 2F
Answer: (b) between F and O
In simple words: A convex lens works like a magnifying glass when the object you want to look at is placed between the focal point (F) and the optical center (O) of the lens. This makes the object appear larger.

🎯 Exam Tip: Understand the different image formations by a convex lens. For magnification, the object must be placed within the focal length (between F and O).

Question 5. The image which cannot be obtained on screen is called
(a) Erect
(b) Real
(c) Virtual
(d) Inverted
Answer: (c) Virtual
In simple words: An image that cannot be caught on a screen, like the image you see in a plane mirror, is called a virtual image. Real images, however, can be projected onto a screen.

🎯 Exam Tip: Differentiate between real and virtual images. Real images can be projected onto a screen, while virtual images cannot and are usually formed when light rays appear to diverge from a point.

Question 6. We are able to see objects around us because
(a) The objects absorb all the light
(b) The light can be reflected
(c) Light travels in straight line
(d) The light reflected from the object enters our eyes.
Answer: (d) The light reflected from the object enters our eyes.
In simple words: We see things because light bounces off them and then travels into our eyes. Our eyes then send signals to our brain to make us see the object.

🎯 Exam Tip: The fundamental principle of vision is that light from an object (either emitted or reflected) must enter the eye for it to be perceived. Reflection is key for non-luminous objects.

Question 7. In whose memory National Science Day is celebrated
(a) Dr.CV Raman
(b) Dr.Chandra Shekhar Bose
Answer: (a) Dr.CV Raman
In simple words: National Science Day is celebrated to remember the great Indian scientist Dr. C.V. Raman for his important work in science, especially his discovery of the Raman effect.

🎯 Exam Tip: This is a general knowledge question about famous scientists and their contributions. Knowing the key achievements of notable figures in science is important.

Question 9. The angle between the incident ray and the reflected ray is
(a) 60°
(b) 90°
(c) 80°
(d) 40°
Answer: (c) 80°
In simple words: The incident ray is the light hitting a surface, and the reflected ray is the light bouncing off. The total angle between these two rays is 80 degrees, which means each ray makes a 40-degree angle with the normal.

🎯 Exam Tip: Remember the Law of Reflection: the angle of incidence is equal to the angle of reflection. If the total angle between incident and reflected rays is given, divide it by two to find the angle of incidence or reflection from the normal.

Question 10. When a ray of light passes through the second optical medium with a change in the angle, the phenomenon is known as
(a) Reflection of light
(b) Absorption of light
(c) Refraction of light
(d) None of the options
Answer: (c) Refraction of light
In simple words: When light changes direction or bends as it moves from one material into another, that event is called refraction.

🎯 Exam Tip: Understand the distinct definitions of reflection, refraction, and absorption. A change in the *angle* of light upon entering a new medium is the hallmark of refraction.

Question 11. The band of seven colours that constitute white light is known as
(a) Rainbow
(b) Palette
(c) Spectrum
(d) None of the options
Answer: (c) Spectrum
In simple words: When white light is split into its full range of seven distinct colours (like red, orange, yellow, green, blue, indigo, and violet), this collection of colours is called a spectrum.

🎯 Exam Tip: Know the specific term for the band of colours produced when white light is dispersed. Rainbow refers to the natural phenomenon, while spectrum is the scientific term for the ordered display of colours.

Question 13. Which of the following is used as a side view mirror?
(a) Plane mirror
(b) Convex mirror
(c) Concave mirror
(d) None of the options
Answer: (b) Convex mirror
In simple words: A convex mirror is used as a side-view mirror in vehicles because it gives a wider view of the area behind the car and always forms an erect, virtual, and diminished image.

🎯 Exam Tip: Remember the properties of different types of mirrors. Convex mirrors are preferred for side-view mirrors because they provide a wider field of view and always produce upright images, although they appear smaller.

Question 14. When an object is placed between focus and optical center of convex lens then the image so formed is
(a) Real and inverted
(b) Real and erect
(c) Erect, virtual and smaller in size
(d) Erect, virtual and magnified
Answer: (d) Erect, virtual and magnified
In simple words: If you place an object very close to a convex lens (between its focus and optical center), the lens will create an image that is upright, not real (virtual), and much larger than the actual object. This is how a magnifying glass works.

🎯 Exam Tip: For convex lenses, remember the specific case where an object placed between F and O results in a virtual, erect, and magnified image on the same side as the object. This is a common application for magnifying glasses.

Question 15. When object lies at 2f in front of a convex lens, its image distance from the lens is at
(a) f
(b) Infinity
(c) Between 2f and infinity
(d) 2f
Answer: (d) 2f
In simple words: When an object is placed at a distance of 2f (twice the focal length) from a convex lens, its image is formed at the same distance of 2f on the other side of the lens. The image will be real, inverted, and the same size as the object.

🎯 Exam Tip: This is a standard ray tracing result for convex lenses. Knowing the image position for an object at 2f is fundamental: the image is also formed at 2f on the opposite side, real, inverted, and same size.

II. Write True Or False In Front I Of The Statements Given Below:
1. Iris in the human eye controls the light entering it. (True/False)
2. Concave lens is known as convergent lens. (True/False)
3. Optic nerve sends messages to the brain. (True/False)
4. Virtual image cannot be formed on a screen. (True/False)
5. A concave lens always formed a virtual, erect and diminished image. (True/False)
6. Real images are always inverted. (True/False)
7. Small hole in Iris is called pupil. (True/False)
8. Shortsightness eye defect persons cannot see nearby objects. (True/False)
9. The high focal length convex lens is used in simple microscope. (True/False)
10. Dr. C.V. Raman was awarded the Bharat Ratna by the Government of India in 1954. (True/False)
Answer:
1. (T)
2. (F)
3. (T)
4. (T)
5. (T)
6. (T)
7. (T)
8. (F)
9. (F)
10. (T)
In simple words: The iris adjusts how much light enters the eye. Concave lenses spread light out, so they are diverging, not converging. The optic nerve transmits visual information to the brain. Virtual images cannot be projected onto a screen. Concave lenses always produce virtual, upright, and smaller images. Real images formed by lenses or mirrors are typically inverted. The small opening in the iris is indeed called the pupil. People with shortsightedness (myopia) have trouble seeing distant objects, not nearby ones. Simple microscopes use convex lenses, but typically with a short focal length for greater magnification, not a high focal length. Dr. C.V. Raman did receive the Bharat Ratna in 1954.

🎯 Exam Tip: Review the basic functions of eye parts, properties of different lenses, characteristics of real and virtual images, and common eye defects. Double-check historical facts carefully.

III. Match Column A And B

Answer:
(i) ↔ (d) Myopia
(ii) ↔ (e) Dispersion
(iii) ↔ (c) [Answer text missing in source]
(iv) ↔ (b) [Answer text missing in source]
(v) ↔ (a) Blind Spot
In simple words: Being able to see close objects but not far ones is called myopia. Dispersion is when white light splits into colours. The blind spot is an area on the retina where the optic nerve connects, and it has no light-sensitive cells. The full definitions for (ii), (iii), (iv) and the corresponding Column B terms for (iii) and (iv) were not completely visible in the original source, but the given matches have been included.

🎯 Exam Tip: Pay attention to the definitions of eye defects, light phenomena, and parts of the eye. Understand which terms relate to vision problems and which describe properties of light.

Refraction Of Light Very Short Answer Type Questions

Question 1. What is light?
Answer: Light is a form of energy that allows us to see the world around us. It travels in waves and is made up of tiny particles called photons. Light helps our eyes detect shapes, colours, and movements.
In simple words: Light is a type of energy that helps us see.

🎯 Exam Tip: For a simple definition, mention that light is a form of energy and its primary function (enabling vision). Briefly stating its dual nature (wave and particle) adds depth.

Question 2. What is dispersion?
Answer: Dispersion is the phenomenon where white light separates into its seven constituent colours (Violet, Indigo, Blue, Green, Yellow, Orange, Red – VIBGYOR) when it passes through a transparent medium like an equilateral prism. This separation occurs because each colour bends at a slightly different angle due to varying speeds within the medium.
In simple words: Dispersion is when white light breaks apart into all its different colours (like a rainbow) after going through a prism.

🎯 Exam Tip: Remember to name the seven colours of the spectrum (VIBGYOR) when defining dispersion. Emphasize that it's white light splitting into its components.

Question 3. What is refractive index?
Answer: The refractive index of a medium is a measure of how much the speed of light changes when it enters that medium from a vacuum (or air, for practical purposes). It is defined as the ratio of the speed of light in air to the speed of light in the medium.
\( \text{Refractive index (of the medium)} = \frac { \text{Speed of light in air} }{ \text{Speed of light in medium} } \)
In simple words: The refractive index tells us how much a material slows down light compared to air. It's found by dividing the speed of light in air by its speed in that material.

🎯 Exam Tip: State the formula clearly, ensuring the ratio is speed in air (or vacuum) over speed in the medium. Note that a higher refractive index means light slows down more.

Question 4. What is Hypermetropia? How is hypermetropia corrected?
Answer: Hypermetropia, also known as longsightedness or farsightedness, is an eye defect where a person can see distant objects clearly but has difficulty seeing nearby objects. This occurs because the eye's lens focuses the light rays behind the retina, instead of directly on it. Hypermetropia can be corrected by using spectacles with a convex lens. The convex lens helps to converge the incoming light rays before they enter the eye, ensuring they focus correctly on the retina, thus restoring clear vision for near objects.
In simple words: Hypermetropia means a person can see far objects well but struggles with close ones. It's fixed using a convex lens in their glasses.

🎯 Exam Tip: Clearly define hypermetropia as difficulty seeing near objects, and remember that it is corrected with a convex (converging) lens to bring the focal point forward onto the retina.

Question. What is lens? How many types of lens are there?
Answer: A lens is a transparent optical medium that has at least one spherical or curved surface. Lenses are used to focus or disperse light rays. There are mainly two types of lenses:
1. Convex (Converging) Lens: This type of lens is thicker in the middle and thinner at the edges. It converges parallel light rays to a single focal point.
2. Concave (Diverging) Lens: This type of lens is thinner in the middle and thicker at the edges. It diverges parallel light rays away from a single focal point.
In simple words: A lens is a clear, curved piece of material that bends light. There are two main kinds: convex lenses, which bring light together, and concave lenses, which spread light out.

🎯 Exam Tip: When defining a lens, mention its transparent and curved nature. Clearly distinguish between convex and concave lenses by describing their shape and their effect on parallel light rays (converging vs. diverging).

Question 6. Why is convex lens called converging lens?
Answer: A convex lens is called a converging lens because when parallel rays of light pass through it, they bend and meet at a single point on the principal axis, known as the focal point. This action of bringing light rays together (converging them) is why it gets its name. This property is due to its shape, being thicker in the middle and thinner at the edges, which causes light rays to bend inwards.
In simple words: A convex lens is called a converging lens because it makes all the parallel light rays that pass through it come together and meet at one spot.

🎯 Exam Tip: The key reason for a convex lens being called a converging lens is its ability to make parallel light rays converge (meet) at a single point after refraction.

Question 7. Define the following terms:
1. Principal axis
2. Optical center
3. Focus
4. Focal length
Answer:
1. Principal axis: This is an imaginary straight line that passes through the centers of curvature of both spherical surfaces of a lens. It is a central line that serves as a reference for understanding how light travels through the lens.
2. Optical center: This is a point on the principal axis located inside the lens. A light ray passing directly through the optical center of the lens does not deviate from its original path.
3. Focus: For a convex lens, the focus (F) is the point on the principal axis where light rays parallel to the principal axis converge after refraction through the lens. For a concave lens, it is the point from which parallel light rays appear to diverge after refraction.
4. Focal length: This is the distance between the optical center of a lens and its principal focus (F). It is denoted by 'f'. For a spherical lens, the focal length is half the radius of curvature \( (f = r/2) \).
In simple words: The principal axis is a straight line through the middle of the lens. The optical center is a point in the lens where light passes straight through without bending. The focus is the point where light rays meet (or seem to meet) after going through the lens. Focal length is the distance from the optical center to the focus.

🎯 Exam Tip: Clearly define each term, perhaps with a simple diagram in mind. Understand the relationship between focal length and radius of curvature. Use precise language for each definition.

Question 9. What type of image is formed at retina?
Answer: The image formed on the retina of the human eye is real, inverted (upside down), and diminished (smaller than the actual object). Even though the image is inverted on the retina, our brain processes the visual information to perceive the world as upright.
In simple words: The image formed on the retina is real, upside-down, and smaller than the actual object. Our brain then flips it so we see things the right way up.

🎯 Exam Tip: Remember the three key characteristics of the image formed on the retina: real, inverted, and diminished. This is a common fact about human vision.

Question 10. What is blind spot?
Answer: The blind spot is a small area on the retina of the human eye where the optic nerve connects and exits the eyeball. This region does not contain any photoreceptor cells (rods and cones), which are responsible for detecting light. Therefore, any light rays that fall on the blind spot cannot be detected, making it insensitive to light and resulting in a small 'blind' area in our field of vision.
In simple words: The blind spot is a tiny part of the retina where the eye's nerve leaves the eye. Because there are no light sensors there, you can't see anything that lands on that specific spot.

🎯 Exam Tip: Define the blind spot by its location (where the optic nerve leaves the retina) and its key characteristic (lack of photoreceptors, making it insensitive to light).

Question 11. When an object is placed within the focal length of the convex lens, where does its image will form?
Answer: When an object is placed within the focal length (between the optical center and the principal focus F) of a convex lens, the image formed is virtual, erect (upright), and magnified (larger than the object). This image appears on the same side of the lens as the object. This is the principle behind how a magnifying glass works.
In simple words: If an object is put very close to a convex lens, inside its focal point, the image will appear big, upright, and not real. It will also be on the same side of the lens as the object.

🎯 Exam Tip: This is a crucial case for convex lenses. Remember that an object within the focal length always produces a virtual, erect, and magnified image on the same side as the object.

Question 12. What is the cause of refraction?
Answer: The primary cause of refraction is the change in the speed of light as it passes from one transparent medium to another. When light enters a medium where its speed is different (either slower or faster) and it hits the boundary at an angle, it changes direction or bends. This change in speed causes the phenomenon of refraction. For instance, light slows down when entering a denser medium like water from air, causing it to bend.
In simple words: Refraction happens because light changes its speed when it moves from one material into another. This change in speed makes the light bend.

🎯 Exam Tip: Focus on the change in the *speed* of light as the fundamental cause of refraction. Mentioning different optical mediums and the angle of incidence adds completeness.

Question 13. Write atleast three effects of refraction of light in our day to day life?
Answer: Refraction of light produces many noticeable effects in our daily lives:
1. An object placed under water appears to be raised from its actual position, making it look shallower than it is.
2. A swimming pool or a bucket of water often appears shallower than its real depth due to this effect.
3. Stars appear to twinkle in the night sky because light from distant stars is continuously refracted by Earth's turbulent atmosphere.
4. A stick or pencil partially immersed in water appears to be bent or broken at the water surface.
In simple words: We see many effects of light bending (refraction) every day. Things in water look higher or bent. Stars twinkle because of light bending in the air. Water bodies seem shallower than they really are.

🎯 Exam Tip: Provide clear and distinct examples. Focus on effects that are easily observable and relate directly to light passing through different mediums (air, water, atmosphere).

Question 14. A ray of light goes from a denser medium to a rarer medium, will it bend towards the normal or away from the normal?
Answer: When a ray of light travels from a denser medium (like glass) to a rarer medium (like air), it bends away from the normal. This happens because light speeds up as it enters the rarer medium, causing it to refract outwards, away from the imaginary line perpendicular to the surface. If the angle is large enough, total internal reflection can occur.
In simple words: When light goes from a thick material to a thin material, it bends away from the normal line.

🎯 Exam Tip: Clearly state that light bends *away from the normal* when moving from a denser to a rarer medium. This is a key rule of refraction, opposite to moving from rarer to denser.

Question 15. Give two uses of convex lens.
Answer: Two common uses of a convex lens are:
1. As a magnifying glass: When an object is placed within its focal length, a convex lens produces a virtual, erect, and magnified image, making it useful for magnifying small objects or text.
2. In spectacles for correcting hypermetropia: Convex lenses are used to correct longsightedness (hypermetropia), where the eye's natural lens is unable to converge light sufficiently, causing distant objects to focus behind the retina. The convex lens helps to converge the light rays onto the retina.
In simple words: Convex lenses are used as magnifying glasses to make small things look bigger. They are also used in glasses to help people with longsightedness see close-up things clearly.

🎯 Exam Tip: For each use, briefly explain *why* a convex lens is suitable by mentioning the specific image properties it creates or the vision defect it corrects.

Refraction Of Light Short Answer Type Questions

Question 1. Draw a ray diagram, for the image formation of an object when it is placed at
1. F
2. In between F and O. Write its nature of the image.
Answer:
1. When an object is placed at F (the principal focus) of a convex lens, the refracted rays become parallel to each other. Consequently, the image is formed at infinity. The nature of this image is real, inverted, and highly magnified.

2. When an object is placed between F (principal focus) and O (optical center) of a convex lens, the image is formed on the same side of the lens as the object. This image is virtual, erect, and magnified (larger than the object). This specific setup is used in magnifying glasses.

In simple words: When an object is at the focal point (F) of a convex lens, the light rays become parallel after passing through the lens, so the image appears infinitely far away and is very big and upside-down. If the object is placed between F and the center of the lens (O), the image appears on the same side, it's upright, not real, and much larger, just like when you use a magnifying glass.

🎯 Exam Tip: For ray diagrams, always draw the principal axis, optical center, and focal points (F and 2F). Use at least two principal rays to locate the image. Clearly label the object, image, and all key points. Make sure arrowheads show the direction of light. For virtual images, use dashed lines for the extended rays.

Question 3. Write a short note on Dr. C.V. Raman.
Answer: Dr. C.V. Raman was a well-known Indian physicist. He was honored with the prestigious Nobel Prize in Physics in 1930 because of his outstanding work on how light scatters. The discovery he made about light scattering is famously known as the Raman effect. He also received the Bharat Ratna in 1954 and the Lenin Peace Prize in 1957. To remember his contributions, National Science Day is celebrated every year in India. His research helped us understand more about the nature of light and how it interacts with matter.
In simple words: Dr. C.V. Raman was an Indian physicist who won the Nobel Prize in 1930 for discovering the Raman effect, which explains how light scatters. National Science Day is celebrated in India every year to honor him.

🎯 Exam Tip: When writing about famous scientists, remember to include their nationality, main achievement (like the Raman effect), and any major awards or honors they received.

Question 4. Why is pencil immersed under water appears to be bent?
Answer: A pencil appears bent when placed in water because of the refraction of light. Refraction happens when light rays travel from one medium (like water) to another (like air) and change their speed and direction. When light from the part of the pencil in the water travels into the air and reaches our eyes, it bends away from the normal. This bending makes our eyes perceive the submerged part of the pencil in a different position, making it look bent or broken. This visual trick is similar to how a coin at the bottom of a pool looks closer than it really is.
In simple words: A pencil in water looks bent because light bends when it moves from water to air. This bending of light is called refraction, and it makes the pencil appear to be in a different place than it actually is.

🎯 Exam Tip: Always use the term "refraction of light" to explain why objects look bent or shifted when viewed through water. Explain that light changes direction when passing between different mediums.

Question 5. Why is concave lens called diverging lens?
Answer: A concave lens is called a diverging lens because it spreads out light rays that pass through it. When parallel rays of light hit a concave lens, they bend outwards after refraction. If you trace these spread-out rays backward, they appear to meet at a single point called the principal focus. Because the lens makes the light rays spread apart, or diverge, it is known as a diverging lens. Unlike a magnifying glass, a diverging lens makes objects look smaller.
In simple words: A concave lens is a diverging lens because it causes parallel light rays to spread out after passing through it. It makes light move away from a central point.

🎯 Exam Tip: To answer this, define "diverging" in the context of light – meaning light rays spread out. Explain that a concave lens always makes parallel light rays move away from each other after refraction.

Question 7. Draw a ray diagram, when the object is placed between F and 2F. Write the nature of the image so formed.
Answer: When an object is placed between the focal point (F) and twice the focal length (2F) of a convex lens, a specific type of image is formed. The image appears beyond 2F on the other side of the lens. This image is real, which means it can be projected onto a screen. It is also inverted (upside down) and larger in size compared to the actual object. This setup is often used in projectors to create large images from small slides.
In simple words: If you place an object between F and 2F of a convex lens, the image will be real, upside down, and bigger, appearing further away than 2F on the other side.

🎯 Exam Tip: Remember the four key characteristics of the image formed when an object is placed between F and 2F for a convex lens: it is formed beyond 2F, is real, inverted, and magnified.

Question 8. What are the functions of Iris and Pupil in human Eye?
Answer: The iris and pupil are important parts of the human eye that control how much light enters it. The iris is the colored part of the eye that surrounds the pupil. Its main job is to adjust the size of the pupil based on the brightness of the light. The pupil is the small, dark opening in the center of the iris. In bright conditions, the iris contracts, making the pupil smaller to reduce the amount of light entering the eye. Conversely, in dim light, the iris relaxes and expands the pupil, allowing more light to enter so we can see better. This clever adjustment helps us see clearly in different lighting conditions and protects our eyes from too much light.
In simple words: The iris changes the size of the pupil to control how much light enters the eye. The pupil is the opening that lets light into the eye.

🎯 Exam Tip: Clearly state that the iris controls the pupil's size, and the pupil is the opening for light. Mention how they adjust in bright versus dim light.

Question 9. What are the causes for short sightedness?
Answer: Short-sightedness, also known as myopia, occurs due to two main reasons. Firstly, the eye lens may have too much converging power because its focal length is too short. This means it bends light more sharply than needed. Secondly, the eyeball itself might be too long from front to back. In both cases, light focuses in front of the retina instead of directly on it, causing distant objects to appear blurry. This condition often appears during childhood or adolescence and tends to stabilize in early adulthood.
In simple words: Short-sightedness happens because the eye lens bends light too much (short focal length) or the eyeball is too long. Both make light focus before it reaches the retina.

🎯 Exam Tip: Remember the two primary causes of short-sightedness: a very curved lens (high converging power/short focal length) and an elongated eyeball.