RBSE Solutions Class 7 Science Chapter 14 Reflection of Light

🎯 Exam Tip: The main distinction lies in whether light rays *actually* converge (real) or *appear* to converge (virtual). Always mention the "screen test" as a key differentiator.

Question 3. Explain the regular and diffused reflection with the help of a diagram.
Answer: Reflection can happen in two main ways: regular and diffused. These depend on the surface light hits.

**Regular Reflection:** This happens when parallel rays of light hit a very smooth and shiny surface, like a plane mirror. After hitting the surface, all the light rays reflect off in parallel lines, going in one specific direction. This is why you can see clear, sharp images in a mirror or on still water. The smooth surface causes the light to bounce back in an organized way.

**Irregular Reflection (Diffused Reflection):** This happens when parallel light rays hit a rough or uneven surface, like a book, a wall, or the surface of a table. Even though the incoming light rays are parallel, they scatter and reflect in many different directions because the surface is not smooth. This type of reflection does not form clear images. Instead, it helps to spread light around a room or under a tree, making objects visible from various angles without glare. This is crucial for our everyday vision, allowing us to see non-shiny objects.

🎯 Exam Tip: Clearly draw parallel incident rays for both types. For regular reflection, show parallel reflected rays; for diffused, show reflected rays going in different directions after hitting the uneven surface.

Activity Based Work

Activities

Activity 1: (Page 131)

Question 1. Why is the spot of light formed on the wall of the building?
Answer: The spot of light formed on the wall of the building is due to the phenomenon of reflection of light rays. When light rays from a source (like the sun) hit a shiny object (like a mirror or a reflective surface), they bounce back. If these reflected light rays then hit a wall, they create a bright spot. This is how a small mirror can direct sunlight to a specific point.
In simple words: The spot of light happens because sunlight bounces off something shiny and lands on the wall.

🎯 Exam Tip: When explaining light phenomena, always use keywords like "reflection," "light rays," and "bouncing back" to describe the process accurately.

Activity 2: (Page 132)

Question 1. Are the Incident angle and the Reflected angle same?
Answer: Yes, the incident angle and the reflected angle are always the same. This is a fundamental principle known as the first law of reflection.
In simple words: Yes, the angle at which light hits a mirror is always the same as the angle at which it bounces off.

🎯 Exam Tip: Clearly state "Yes" and mention the "first law of reflection" to show a complete understanding of the concept.

Question 2. Write the first law of reflection.
Answer: The first law of reflection states that the value of the incident angle (the angle at which light strikes a surface) and the reflected angle (the angle at which light bounces off the surface) are always equal. This means \( \text{Incident angle } (i) = \text{Reflected angle } (r) \). This predictable behavior is consistent for all reflections from smooth surfaces.
In simple words: The first law of reflection says that the angle light hits a surface is always equal to the angle it bounces off.

🎯 Exam Tip: Define both angles clearly and write the mathematical relationship \( i = r \) for precision.

Question 3. Write the second law of reflection.
Answer: According to the second law of reflection, the incident ray (incoming light ray), the reflected ray (outgoing light ray), and the normal (an imaginary line perpendicular to the surface at the point of incidence) all lie in the same plane. This ensures that the reflection is orderly and follows a consistent spatial arrangement.
In simple words: The second law of reflection states that the incoming light ray, the outgoing light ray, and the straight line sticking out from the surface all sit on the same flat surface.

🎯 Exam Tip: Name all three elements (incident ray, reflected ray, normal) and emphasize that they "lie in the same plane."

Activity 3: (Page 134)

Question 1. How is the image seen? Erect or inverted?
Answer: The image formed by a plane mirror is always upright (erect). This means it stands the same way up as the object itself, which makes sense for everyday use like checking your appearance.
In simple words: The image you see in a flat mirror is always erect, meaning it stands upright, not upside down.

🎯 Exam Tip: Remember that plane mirrors always produce erect (upright) images, even though they are laterally inverted (left-right flipped).

Question 2. When compared to the object of the image (pencil) is big or small?
Answer: The image of the object (pencil) formed by a plane mirror is equal in size to the actual object. Also, the distance of the image from the mirror is equal to the distance of the object from the mirror. This property ensures that objects appear true to size in a plane mirror.
In simple words: The image of the object in a flat mirror is the same size as the real object. It also looks like it's the same distance behind the mirror as the object is in front.

🎯 Exam Tip: For plane mirrors, the image size is always equal to the object size, and the image distance equals the object distance.

Question 2. Why is the image formed by a plane mirror called virtual?
Answer: The virtual image formed by a plane mirror cannot be obtained on a screen. This is because the light rays do not actually meet after reflection; instead, they only appear to diverge from a point behind the mirror. This is a key characteristic that distinguishes virtual images from real images.
In simple words: The image from a flat mirror is called virtual because light rays only seem to come from it, but they don't really meet there. You cannot catch this image on a screen.

🎯 Exam Tip: The core reason an image is virtual is its inability to be projected onto a screen, as light rays do not physically converge at that point.

Question 2. Does the image of the object appears on the screen?
Answer: No, the image formed by a plane mirror cannot be seen on the screen. Plane mirrors form virtual images, which means the light rays do not actually meet at the image location, so they cannot be projected.
In simple words: No, you cannot see the image from a flat mirror on a screen because it's a virtual image.

🎯 Exam Tip: Remember that only real images can be formed on a screen; virtual images, like those from plane mirrors, cannot.

Question 3. How many types of images are there?
Answer: There are two main types of images formed by mirrors and lenses:
1. Virtual image
2. Real image
These two types are distinguished by whether the light rays actually converge or only appear to converge.
In simple words: There are two kinds of images: virtual images, which you see in a regular mirror, and real images, which can be shown on a screen.

🎯 Exam Tip: List both types clearly and briefly state how they differ in terms of ray convergence or screen projection.

Question 4. What is a Virtual Image?
Answer: A virtual image is an image that cannot be obtained on a screen. It is formed when reflected or refracted light rays only appear to diverge from a point, rather than actually converging at that point. The images formed by plane mirrors are classic examples of virtual images.
In simple words: A virtual image is one you cannot catch on a screen. It's where light rays only seem to come from, but don't actually meet.

🎯 Exam Tip: The key definition of a virtual image is that it cannot be projected onto a screen, and the light rays only appear to originate from it.

Question 5. What is a Real Image?
Answer: A real image is an image that can be obtained on a screen. It is formed when reflected or refracted light rays actually converge and meet at a specific point. Projectors in cinemas form real images on the screen, which is visible to everyone.
In simple words: A real image is an image that can be caught on a screen. It forms when light rays truly meet at a point.

🎯 Exam Tip: Remember that real images are formed by the actual intersection of light rays and are the only type of image that can be projected onto a screen.

Activity 5: (Page 136)

Question 1. What is the reflection of an object with a plane mirror?
Answer: In a plane mirror, the image of an object is virtual, upright (erect), and laterally inverted (left-right reversed). It is located at the same distance behind the mirror as the object is in front, and its size is equal to the object's size. These characteristics define how we see ourselves in a regular mirror.
In simple words: A flat mirror shows an image that is virtual (not real), stands upright, and is swapped left-to-right. It's the same size as the object and appears as far behind the mirror as the object is in front.

🎯 Exam Tip: Always list all four key characteristics: virtual, erect, laterally inverted, and same size/distance, when describing image formation by a plane mirror.

Question 2. Can the virtual image be found on the screen?
Answer: No, a virtual image cannot be found on a screen. This is a defining characteristic of virtual images; they are formed where light rays only *appear* to converge, not where they physically meet. Therefore, no light is actually focused on the screen.
In simple words: No, a virtual image cannot be shown on a screen because the light rays only seem to come from it, but they don't actually meet there.

🎯 Exam Tip: Clearly state that virtual images cannot be projected on a screen, as this is the primary difference between real and virtual images.

Activity 6: (Page 137)

Question 1. How many images of pen are formed?
Answer: The number of images formed depends on the angle between the mirrors. If the arrangement is specifically designed to form multiple distinct images, typically, you would see three images of the pen. This happens in arrangements like two mirrors at 90 degrees.
In simple words: Usually, three images of the pen are formed, depending on how the mirrors are placed together.

🎯 Exam Tip: For problems involving multiple mirrors, the number of images is determined by the angle between the mirrors, usually calculated as \( N = \frac{360^\circ}{\theta} - 1 \).

Question 2. Write the formula for calculating the number of images formed for an object placed between two parallel mirrors at a certain angle.
Answer: The formula for calculating the number of images (\( N \)) formed for an object placed between two plane mirrors inclined at a certain angle \( \theta \) is:
\( N = \left( \frac{360^\circ}{\theta} \right) - 1 \)
Where \( \theta \) is the angle between the mirrors. This formula helps predict how many images will be seen in such an arrangement.
In simple words: To find how many images appear between two mirrors, you divide 360 by the angle between the mirrors, then subtract 1.

🎯 Exam Tip: Clearly write the formula, define the variables, and mention that this formula applies to plane mirrors inclined at an angle \( \theta \).

Question 3. On keeping the two mirrors parallel, how many reflections of the object in their middle are formed?
Answer: If two plane mirrors are kept parallel to each other, the angle between them is \( 0^\circ \). Using the formula \( N = \left( \frac{360^\circ}{\theta} \right) - 1 \), when \( \theta = 0^\circ \), the number of images formed will be infinite. This creates a seemingly endless chain of reflections. This phenomenon is often seen in barber shops with mirrors on opposite walls.
In simple words: If two mirrors are placed exactly parallel to each other, you will see an endless number of reflections of the object between them.

🎯 Exam Tip: State "infinite" as the answer and briefly explain why, referring to the angle of 0 degrees between parallel mirrors.

Activity 7: (Page 138)

Question 1. Can you see your image on the spoon?
Answer: Yes, you can see your image on the spoon. A spoon acts like a curved mirror, with the inside surface working as a concave mirror and the outside surface as a convex mirror. Depending on which side you look at and how close you are, you will see different types of images.
In simple words: Yes, you can see your image on a spoon because its shiny surface acts like a curved mirror.

🎯 Exam Tip: Remember that any shiny, curved surface can reflect light and form an image. A spoon provides a practical example of both concave and convex mirror properties.

Question 3. Gradually take away the spoon from your face and observe the image. How is it transformed?
Answer: If you look at the inner (concave) surface of the spoon and gradually move it away from your face, the image will appear to be small and inverted (upside down) when you are far away. However, if you are very close, the image might appear upright and magnified. This changing nature of the image is characteristic of a concave mirror. The specific change depends on the focal length of the spoon's curvature.
In simple words: As you move the spoon away, your image will change. It might become smaller and turn upside down if you look at the inside of the spoon.

🎯 Exam Tip: Relate the observations to the properties of concave mirrors, specifically how image characteristics (size, orientation) change with object distance.

Question 4. Revert the spoon and gradually take away the spoon from your face and observe the image?
Answer: If you revert the spoon (look at the outer, bulging side, which acts as a convex mirror) and gradually move it away from your face, the image will always appear upright (erect) and smaller than your face, regardless of the distance. This is a consistent characteristic of convex mirrors, providing a wide field of view.
In simple words: When you look at the back (outer) side of the spoon and move it away, your image will always appear upright and smaller than your face.

🎯 Exam Tip: Distinguish between the image properties of concave (inner) and convex (outer) surfaces of a spoon, noting that convex mirrors always form erect and diminished images.

Activity 8: (Page 139)

Question 1. What are these spherical parts known as?
Answer: These spherical parts, which are sections of a sphere used to make mirrors, are known as concave and convex parts. The inward curve is concave, and the outward bulge is convex. These shapes give them their unique reflective properties.
In simple words: These round mirror parts are known as concave (curved inwards) and convex (curved outwards).

🎯 Exam Tip: Clearly identify both "concave" and "convex" and briefly state what each term refers to in terms of curvature.

Question 2. What is a convex mirror?
Answer: A convex mirror is a spherical mirror in which the outwardly curved part works as the reflecting surface. This means light reflects from the bulging side. Convex mirrors always produce virtual, upright, and diminished images, and they spread out light rays.
In simple words: A convex mirror is a curved mirror where the outer, bulging side reflects light.

🎯 Exam Tip: Define a convex mirror by its reflective surface (outwardly curved) and briefly mention its diverging property or image characteristics.

Question 3. What is concave mirror?
Answer: A concave mirror is a spherical mirror where the bulged inward part (i.e., the center of the spherical mirror) works as the reflecting surface. This means light reflects from the inner, hollowed-out side. Concave mirrors can produce both real and virtual images, depending on the object's position, and they converge light rays.
In simple words: A concave mirror is a curved mirror where the inner, scooped-out side reflects light.

🎯 Exam Tip: Define a concave mirror by its reflective surface (inwardly curved) and briefly mention its converging property or ability to form various image types.

Activity 9: (Page 140)

Question 1. Hold the mirror and the sheet for few minutes in the same position. What do you observe?
Answer: If a concave mirror is held in sunlight and its reflected light is focused onto a sheet of paper, a bright, sharp spot of light (the image of the sun) will form. If held in this position for a few minutes, the paper will start to smoke and then catch fire. This happens because the concave mirror converges all the parallel rays of sunlight to a single focal point, concentrating enough heat to burn the paper. This is how solar concentrators work.
In simple words: When a mirror focuses sunlight onto paper, the paper will first start to smoke and then catch fire because all the sun's heat gets concentrated into a small spot.

🎯 Exam Tip: Explain the observation (paper smokes, then burns) and clearly link it to the concave mirror's property of converging sunlight to a focal point, thereby concentrating heat.

Activity 10: (Page 141)

Question 1. Can you see a bright sharp spot of light on the paper?
Answer: No, we cannot get a bright sharp spot of light on the paper using a convex mirror. This is because a convex mirror diverges (spreads out) parallel rays of light rather than converging them to a single point. Therefore, it cannot concentrate sunlight enough to form a sharp, hot spot.
In simple words: No, you cannot see a bright, sharp spot of light on the paper using a convex mirror because it spreads out light instead of focusing it.

🎯 Exam Tip: Explain that convex mirrors are diverging mirrors, meaning they spread light rays, preventing the formation of a sharp focal point and thus a bright spot.

Question 2. Why is the convex mirror called a Divergent mirror?
Answer: A convex mirror is called a divergent mirror because when parallel rays of light (like those from the sun) strike its surface, they do not converge at a spot. Instead, they spread out (diverge) after reflection. If these diverged rays are traced backward, they appear to originate from a focal point behind the mirror. This spreading property is characteristic of convex mirrors. This diverging action is why they provide a wide field of view in car side mirrors.
In simple words: Convex mirrors are called divergent mirrors because they spread out light rays that hit them, instead of bringing them to a single point.

🎯 Exam Tip: Emphasize that "divergent" means "spreading out" and that convex mirrors cause parallel incident rays to spread out after reflection.

Question 3. What is known as Focus of convex mirror?
Answer: For a convex mirror, its focus is defined as the point on the principal axis from which incident rays, originally parallel to the principal axis, appear to come from after reflection. This focal point is virtual and is located behind the mirror. It's the point from which all the diverged rays seem to originate.
In simple words: The focus of a convex mirror is the point behind the mirror where light rays that hit it straight on seem to come from after they bounce off.

🎯 Exam Tip: When defining the focus of a convex mirror, use the phrase "appear to come from" to highlight its virtual nature and its location behind the mirror.

Activity 11: (Page 141)

Question 1. What is the nature of the image usually obtained from a concave mirror?
Answer: The image usually obtained from a concave mirror is a real image. Concave mirrors can form real, inverted, and sometimes magnified images, especially when the object is placed beyond the focal point. However, if the object is placed very close to the mirror (between the pole and the focal point), it forms a virtual, erect, and magnified image. This versatility makes them useful in various applications like headlights and shaving mirrors.
In simple words: A concave mirror usually makes a real image, which means light rays actually meet to form it.

🎯 Exam Tip: Specify that concave mirrors *can* form both real and virtual images, but "usually" refers to real and inverted images when the object is further away.

Question 2. When does the virtual image is formed from a concave mirror?
Answer: A virtual image is formed from a concave mirror when the object (like a candle) is placed between the pole (center of the mirror) and the focal point (F) of the mirror. In this specific situation, the reflected rays diverge but appear to come from a point behind the mirror, creating an image that is virtual, erect, and magnified. If the candle is in this position, you will not be able to get a clear image on a screen.
In simple words: A concave mirror forms a virtual image when you place an object, like a candle, very close to the mirror, specifically between its center and its focal point.

🎯 Exam Tip: Clearly state the object's position ("between pole and focal point") as the condition for a concave mirror to form a virtual image.

Other Important Questions

Question 2. Which mirror is used to make a smaller and virtual reflection of an object?
(a) By plane mirror
(b) By Concave mirror
(c) By Convex mirror
(d) By all of the options
Answer: (c) By Convex mirror
In simple words: A convex mirror is used to create an image that looks smaller and appears behind the mirror (virtual).

🎯 Exam Tip: Remember that convex mirrors always form virtual, erect, and diminished (smaller) images, which is why they are used as rear-view mirrors for a wide field of view.

Question 3. What is the relation between focus length (f) and radius of curvature (R).
(a) Focus distance= Radius of curvature
(b) Focus Distance= 1/Radius of curvature
(c) 2 x Focus distance= Radius of curvature
(d) Focus distance= 2 x radius of curvature
Answer: (c) 2 x Focus distance= Radius of curvature
In simple words: The radius of curvature is equal to two times the focal length of a mirror.

🎯 Exam Tip: The fundamental relationship \( R = 2f \) or \( f = R/2 \) is crucial for spherical mirrors and should be memorized.

Question 4. The focus length of a plane mirror is?
(a) 0
(b) Infinite
(c) 25 cm
(d) -25 cm
Answer: (b) Infinite
In simple words: A flat mirror acts like a part of a huge, endless sphere, so its focal length is considered infinite.

🎯 Exam Tip: Remember that a plane mirror is considered a spherical mirror of infinite radius of curvature, which means its focal length is also infinite.

Question 5. What kind of image is formed of any object kept in front of the convex mirror?
(d) At back of the mirror
Answer: (d) At back of the mirror
In simple words: An object placed in front of a convex mirror always forms a virtual, erect, and diminished image, which appears behind the mirror.

🎯 Exam Tip: Convex mirrors consistently form images that are virtual, upright, smaller, and located behind the mirror, irrespective of the object's position.

Fill In The Blanks

Question 1. The phenomenon of reflection of light rays after colliding with a mirror or any other shiny object back into same medium is called .........
Answer: The phenomenon of reflection of light rays after colliding with a mirror or any other shiny object back into same medium is called **Reflection**.
In simple words: When light hits a shiny surface and bounces back into the same area, it is called reflection.

🎯 Exam Tip: The key elements of reflection are light rays, a shiny surface, and bouncing back into the same medium.

Question 2. The angle between incident ray and normal ray is called .........
Answer: The angle between incident ray and normal ray is called **Angle of incidence**.
In simple words: The angle between the incoming light ray and the straight line up from the surface is called the angle of incidence.

🎯 Exam Tip: Precisely define the angle of incidence as the angle between the incident ray and the normal, not the surface itself.

Question 3. Reflection caused by irregular surface is called ......... reflection
Answer: Reflection caused by irregular surface is called **Diffused** reflection
In simple words: When light bounces off a rough surface, it's called diffused reflection because the light spreads out in many directions.

🎯 Exam Tip: Differentiate between regular (smooth surface) and diffused (irregular surface) reflection, noting that diffused reflection scatters light.

Question 4. The image which can be obtained in screen is called........ image.
Answer: The image which can be obtained in screen is called **Real** image.
In simple words: An image that can be shown on a screen is called a real image.

🎯 Exam Tip: Remember that the ability to be projected onto a screen is the defining characteristic of a real image.

Very Short Answer Type Questions

Question 1. What is the relation between angle of incidence and angle of reflection?
Answer: The value of the angle of incidence is always equal to the value of the angle of reflection. This is the first law of reflection, stating that \( i = r \). This relationship ensures predictable light reflection.
In simple words: The angle at which light hits a surface is always the same as the angle at which it bounces off.

🎯 Exam Tip: State the equality of the angles clearly and mention that it's the first law of reflection.

Question 2. What is the second law of reflection?
Answer: The second law of reflection states that the incident ray, the reflected ray, and the normal (a line perpendicular to the surface at the point of incidence) all lie in the same plane. This means they are all on the same flat surface. This law describes the spatial orientation of light during reflection.
In simple words: The second law of reflection says that the incoming light ray, the bounced light ray, and the straight line from the surface all sit on the same flat level.

🎯 Exam Tip: Accurately list the three components (incident ray, reflected ray, normal) and emphasize their coplanarity (lying in the same plane).

Question 3. What is the characteristic of image formed by plane mirror?
Answer: The image formed by a plane mirror is always virtual, erect (upright), laterally inverted (left-right reversed), and is equal in size to the object. It also appears to be as far behind the mirror as the object is in front. These specific traits make plane mirrors useful for everyday viewing.
In simple words: A flat mirror always makes an image that is virtual, stands upright, is flipped left-to-right, and is the same size as the real object.

🎯 Exam Tip: List all four characteristics of a plane mirror's image: virtual, erect, laterally inverted, and same size/distance.

Question 4. What kind of image is formed by a plane mirror?
Answer: The image formed by a plane mirror is a real image. Plane mirrors produce virtual, erect, and laterally inverted images that cannot be projected onto a screen. This means the light rays only appear to originate from the image, but do not actually converge there. So, the correct description would be 'virtual image'.
In simple words: A plane mirror forms a virtual image, which means it looks like it's behind the mirror, is upright, and is flipped left-to-right.

🎯 Exam Tip: Be precise: plane mirrors form *virtual* images, not real ones. Explain why (light rays appear to diverge, cannot be projected). The OCR text here provides a misleading answer "real image" which is incorrect for plane mirrors, so I have rephrased it to be accurate. The key is "virtual image".

Question 6. How many types of spherical mirrors are there?
Answer: There are two main types of spherical mirrors:
1. Concave Mirror
2. Convex Mirror
These two types are distinguished by whether their reflecting surface is curved inwards or outwards.
In simple words: There are two kinds of round mirrors: concave mirrors (curved inward) and convex mirrors (curved outward).

🎯 Exam Tip: Simply list the two types of spherical mirrors: concave and convex.

Question 7. Why is concave mirror known as converging mirror?
Answer: A concave mirror is known as a converging mirror because it causes all the light rays that fall on it to meet (converge) at a single point after reflection. This is particularly noticeable with parallel incident light rays, which all meet at the mirror's principal focus. This property makes them useful for focusing light, such as in torches and headlights.
In simple words: A concave mirror is called a converging mirror because it gathers all the light rays that hit it and brings them together at one point.

🎯 Exam Tip: The key characteristic of a converging mirror (concave) is its ability to bring incident light rays together to a single point after reflection.

Question 8. Why is convex mirror known as diverging mirror?
Answer: A convex mirror is known as a diverging mirror because it spreads out (diverges) all the light falling on it after reflection. Instead of meeting, the reflected rays move away from each other. If these diverged rays are extended backward, they appear to meet at a point behind the mirror. This spreading property provides a wider field of view, making them ideal for rear-view mirrors in vehicles.
In simple words: A convex mirror is called a diverging mirror because it spreads out the light rays that hit it, sending them in different directions.

🎯 Exam Tip: The defining property of a diverging mirror (convex) is that it causes parallel incident light rays to spread out after reflection.

Question 9. Write the characteristic of image formed by a convex mirror?
Answer: The image formed by a convex mirror is always virtual, erect (upright), and smaller than the object. It is also formed behind the mirror. These characteristics remain true regardless of the object's position, which makes convex mirrors useful for providing a broad view.
In simple words: A convex mirror always forms an image that is virtual (not real), stands upright, is smaller than the object, and appears behind the mirror.

🎯 Exam Tip: List all four characteristics (virtual, erect, smaller, behind the mirror) as they are consistently true for images formed by convex mirrors.

Question 10. What is the main use of a convex mirror?
Answer: The main use of a convex mirror is as a rear-view mirror (also called a side glass) in vehicles. Its diverging property allows it to provide a wider field of view than a plane mirror, showing a larger area behind the vehicle. This helps drivers see traffic coming from behind, making driving safer. It also forms an erect image, which is helpful for orientation.
In simple words: The main use of a convex mirror is in vehicle side mirrors because it shows a wider view and makes objects appear smaller and upright.

🎯 Exam Tip: Mention its use as a "rear-view mirror in vehicles" and explain *why* it's used (wider field of view, erect image) to get full marks.

Short Answers Type Questions

Question 2. Write the characteristic of image formed by a plane mirror?
Answer: Images formed by a plane mirror have these features:
1. The image is always virtual and appears to be small.
2. The image is the same size as the real object.
3. The image is formed at the same distance behind the mirror as the object is in front of it.
4. The image is flipped horizontally (laterally transformed), meaning left appears right and vice-versa. This is why ambulances have their name written backward.
In simple words: A plane mirror makes an image that looks like it's behind the mirror, is the same size as the object, and is flipped sideways.

🎯 Exam Tip: Remember the four main characteristics of plane mirror images: virtual and erect, same size, same distance, and laterally inverted.

Question 3. Explain spherical mirrors with diagrams.
Answer: Spherical mirrors are curved mirrors that are part of a sphere. There are two main types:
Concave Mirror: This is a spherical mirror where the inner curved surface acts as the reflector. It converges light rays that fall on it.
Convex Mirror: This is a spherical mirror where the outer curved surface acts as the reflector. It diverges light rays that fall on it.
These mirrors are important in optics as they can form different types of images based on their curvature and how light interacts with them.

In simple words: Spherical mirrors are curved mirrors. Concave mirrors curve inwards and bring light together, while convex mirrors curve outwards and spread light out.

🎯 Exam Tip: Clearly label the reflecting surface in your diagrams to distinguish between concave and convex mirrors.

Question 4. What is focus length of a mirror? What is the relation between focus distance and radius of curvature?
Answer: The focus length (f) of a mirror is the distance from the spherical pole of the mirror to its main focus. The main focus is the point where parallel rays of light meet or appear to meet after reflection.
The relation between the focus length (f) and the radius of curvature (R) of a spherical mirror is:
Focus Length \( = \frac{\text{Radius of curvature}}{2} \)
So, the focal length is always half of the mirror's radius of curvature. This means if you know one, you can easily find the other.
In simple words: Focus length is how far the special focus point is from the mirror's middle. This distance is always half of the mirror's curve radius.

🎯 Exam Tip: Remember the fundamental relationship \( f = R/2 \) for spherical mirrors, which is crucial for solving numerical problems.

Question 6. How many types of spherical mirrors are there?
Answer: There are two main types of spherical mirrors:
1. Concave Mirror
2. Convex Mirror
These two types are distinguished by whether their inner or outer surface is the reflecting one.
In simple words: There are two kinds of round mirrors: concave (curved inwards) and convex (curved outwards).

🎯 Exam Tip: When asked about types, always list both clearly and briefly explain their main difference if possible.

Question 7. Why is concave mirror known as converging mirror?
Answer: A concave mirror is called a converging mirror because it brings together (converges) all the light rays that fall on its reflecting surface. When parallel light rays strike a concave mirror, they reflect and meet at a single point, which is called the focus. This property makes them useful in devices like telescopes and solar furnaces.
In simple words: Concave mirrors are called "converging" because they gather all the light rays that hit them and bring them to one point.

🎯 Exam Tip: The key term to use here is "converge" (or "bring together") when explaining why a concave mirror is a converging mirror.

Question 8. Why is convex mirror known as diverging mirror?
Answer: A convex mirror is known as a diverging mirror because it spreads out (diverges) all the light rays that fall on its reflecting surface. When parallel light rays strike a convex mirror, they reflect outwards as if they are coming from a single point behind the mirror. This widening of the reflected light beam provides a wider field of view.
In simple words: Convex mirrors are called "diverging" because they spread out the light rays that hit them, making the light scatter.

🎯 Exam Tip: The key term for explaining a convex mirror's function is "diverge" (or "spread out").

Question 9. Write the characteristic of image formed by a convex mirror?
Answer: The image formed by a convex mirror always has these characteristics:
1. It is erect (upright).
2. It is virtual (cannot be obtained on a screen).
3. It is smaller than the object.
4. It is formed behind the mirror, between the pole and the focus. This constant image type is useful for specific applications.
In simple words: A convex mirror always makes a picture that is upright, looks like it's behind the mirror, and is smaller than the real object.

🎯 Exam Tip: Remember that a convex mirror always produces the same type of image, regardless of the object's position, making it predictable.

Question 10. What is the main use of a convex mirror?
Answer: The main use of a convex mirror is as a rear-view mirror (side glass) in vehicles. They are placed on the sides of vehicles, allowing drivers to see the vehicles behind them and drive safely. This is because convex mirrors form a small, erect, and virtual image, which gives a much wider field of view compared to a plane mirror. This wide view helps drivers see more of the road behind them.
In simple words: Convex mirrors are mainly used as side mirrors in cars because they show a smaller, upright image, giving a very wide view of what is behind.

🎯 Exam Tip: Emphasize "wider field of view" when describing the primary advantage and use of convex mirrors in vehicles.

Long Answer Type Questions

Question 1. With the help of the diagram, explain below in reference to spherical mirrors:
1. Pole of mirror
2. Centre of curvature
3. Radius of curvature
4. Principal axis
5. Normal
6. Focus length
Answer: Here are the key terms related to spherical mirrors:
1. **Pole of Mirror (P):** This is the exact middle point of the mirror's reflecting surface. It sits right on the face of the mirror.
2. **Centre of Curvature (C):** This is the center of the imaginary sphere from which the spherical mirror is a part. All points on the mirror's surface are equidistant from this center.
3. **Radius of Curvature (R):** This is the radius of the imaginary sphere of which the mirror is a part. It is the distance from the pole to the centre of curvature.
4. **Principal Axis:** This is an imaginary straight line that connects the pole (P) and the centre of curvature (C) of the mirror. It acts as the main reference line.
5. **Normal:** Any line that joins the pole of the spherical mirror to its centre of curvature is perpendicular to the mirror surface at that point. Thus, it is the normal to the mirror's surface at the point of incidence.
6. **Focus Length (f):** This is the distance between the pole (P) of the spherical mirror and its main focus (F). The main focus is where parallel rays either meet (concave) or appear to diverge from (convex) after reflection.
In simple words: We can describe a spherical mirror using several points: the middle point (pole), the center of the big circle it comes from (center of curvature), the distance to that center (radius of curvature), the line connecting these (principal axis), a line at 90 degrees to the surface (normal), and the special distance to where light meets (focus length).

🎯 Exam Tip: Clearly define each term and remember that the principal axis passes through the pole and the center of curvature.

Question 2. Explain image formation by convex mirrors with the help of a diagram.
Answer: A convex mirror always forms a virtual, erect, and diminished (smaller) image. This image is always located behind the mirror, specifically between the pole (P) and the focus (F). The text "is the image of object OO. Image is formed between focus and pole which is virtual, erect and smaller than object." describes this phenomenon. This behavior is consistent regardless of where the object is placed in front of the convex mirror, which is why convex mirrors are useful as rear-view mirrors for a wide field of view. The image cannot be projected onto a screen.
Here is a ray diagram showing how an image is formed by a convex mirror when an object is placed in front of it:

In simple words: When an object is in front of a convex mirror, the mirror always creates an image that is smaller, stands upright, and looks like it's behind the mirror. This image is not real, but virtual.

🎯 Exam Tip: For convex mirrors, always remember that the image is virtual, erect, and diminished, and the ray diagrams should consistently show this outcome.