Maharashtra Board Class 8 Science Chapter 16 Reflection of Light Solutions

Std 8 Science Chapter 16 Reflection Of Light Question Answer Maharashtra Board

Class 8 Science Chapter 16 Reflection Of Light Question Answer Maharashtra Board

1. Fill In The Blanks:

 

Question i. The perpendicular to the mirror at the point of incidence is called ............
Answer: The perpendicular to the mirror at the point of incidence is called the normal.
In simple words: The normal is the line that stands perpendicular to the mirror surface at the point where a light ray hits it.

🎯 Exam Tip: Understanding the concept of the 'normal' is crucial as it serves as a reference line for measuring angles of incidence and reflection.

 

Question ii. The reflection of light from a wooden surface is ............ reflection.
Answer: The reflection of light from a wooden surface is irregular reflection.
In simple words: A rough surface like wood scatters light in many directions, resulting in irregular reflection.

🎯 Exam Tip: Differentiating between regular and irregular reflection based on surface properties is a key concept for understanding how we see objects.

 

Question iii. The working of a kaleidoscope is based on the properties of ............
Answer: The working of a kaleidoscope is based on the properties of reflection of light.
In simple words: A kaleidoscope uses multiple mirrors to reflect light and create symmetrical, ever-changing patterns.

🎯 Exam Tip: Recognize that optical instruments like the kaleidoscope and periscope operate on the fundamental principle of light reflection.

 

Question 2. Draw a figure describing the following: The reflecting surfaces of two mirrors make an angle of 90° with each other. If a ray incident on one mirror has an angle of incidence of 30°, i draw the ray reflected from the second mirror. What will be its angle of reflection?

 

Question a. Draw a figure describing the following: The reflecting surfaces of two mirrors make an angle of 90° with each other. If a ray incident on one mirror has an angle of incidence of 30°, draw the ray reflected from the second mirror. What will be its angle of reflection?
Answer: For the ray C, the angle of reflection = \(60^\circ\).
ℹ️ चित्र व्याख्या (Diagram Explanation): इस चित्र में दो दर्पण \(M_1\) और \(M_2\) दिखाए गए हैं जो एक-दूसरे के साथ \(90^\circ\) का कोण बनाते हैं। एक प्रकाश किरण \(A\) दर्पण \(M_1\) पर \(30^\circ\) के आपतन कोण पर पड़ती है। \(N_1\) दर्पण \(M_1\) पर अभिलंब है। यह किरण \(B\) के रूप में परावर्तित होती है, जो दर्पण \(M_2\) पर आपतित होती है। \(N_2\) दर्पण \(M_2\) पर अभिलंब है। अंत में, किरण \(B\) दर्पण \(M_2\) से \(C\) के रूप में परावर्तित होती है, जिसका परावर्तन कोण \(60^\circ\) है।
In simple words: When light hits a mirror, it reflects; if it then hits a second mirror, it reflects again, and we can calculate the new angle of reflection using the laws of reflection and geometry.

🎯 Exam Tip: For problems involving multiple reflections, carefully apply the laws of reflection at each surface, remembering that the angle of incidence equals the angle of reflection.

 

Question 3. How will you explain the statement 'We cannot see the objects in a dark room'?

 

Question a. How will you explain the statement 'We cannot see the objects in a dark room'?
Answer: In a room that is completely dark, no light falls on objects. Hence, no light enters our eyes. Hence, there is no sensation of vision, i.e., we cannot see the objects.
In simple words: We see objects because light reflects off them and enters our eyes; in total darkness, there's no light to reflect, so we can't see.

🎯 Exam Tip: Emphasize that vision fundamentally depends on light reflecting from objects and reaching our eyes, not just the presence of objects.

 

Question 4. Explain the difference between regular and irregular reflection of light.

 

Question a. Explain the difference between regular and irregular reflection of light.
Answer: For regular reflection of light, the angles of incidence as well as the angles of reflection are the same for all parallel rays of light incident on the plane and smooth surface. Hence, the reflected rays are also parallel to one another.
For irregular reflection of light, the angles of incidence for parallel rays of light incident on the rough surface are not equal, and hence the angles of reflection are also not equal. Here, the reflected rays are not parallel to one another and spread over a large surface.
In simple words: Regular reflection occurs on smooth surfaces, producing parallel reflected rays, while irregular reflection happens on rough surfaces, scattering reflected rays in many directions.

🎯 Exam Tip: Clearly distinguish between the surface types (smooth vs. rough) and the resulting behavior of reflected parallel light rays (parallel vs. scattered) to explain regular and irregular reflection.

 

Question 5. Draw a figure showing the following: (a) Incident ray, (b) Normal, (c) Angle of incidence, (d) Angle of reflection, (e) Point of incidence, (f) Reflected ray.

 

Question a. Draw a figure showing the following:
(a) Incident ray
(b) Normal
(c) Angle of incidence
(d) Angle of reflection
(e) Point of incidence
(f) Reflected ray.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र प्रकाश के परावर्तन के मुख्य घटकों को दर्शाता है। एक समतल दर्पण \(PQ\) पर एक आपतित किरण \(A\) बिंदु \(O\) पर आपतित होती है। बिंदु \(O\) पर दर्पण के लंबवत खींची गई रेखा \(N\) अभिलंब कहलाती है। आपतित किरण और अभिलंब के बीच का कोण \(i\) आपतन कोण है। परावर्तित किरण \(B\) अभिलंब के साथ एक कोण \(r\) बनाती है, जिसे परावर्तन कोण कहते हैं।
In simple words: The diagram illustrates how light reflects from a surface, showing the path of the incident ray, the reflected ray, the normal, and the angles of incidence and reflection.

🎯 Exam Tip: Accurately labeling the incident ray, reflected ray, normal, point of incidence, and the angles of incidence and reflection is essential for drawing correct reflection diagrams.

 

6. Study The Following Incident.

Swara and Yash were looking in a water-filled vessel. They could see their images clearly in the still water. At that instant, Yash threw a stone in the water. Now their images were blurred. Swara could not understand the reason for the blurring of the images. Explain the reason for blurring of the images to Swara by answering the following questions:

 

Question i. Is there a relation between the reflection of light and the blurring of the images?
Answer: Yes.
In simple words: The clarity of an image formed by reflection is directly affected by how smoothly or irregularly the light reflects off the surface.

🎯 Exam Tip: Recognize that any disturbance to a reflecting surface, like ripples in water, can change the nature of reflection from regular to irregular, affecting image quality.

 

Question ii. Which types of reflection of light can you notice from this?
Answer: Regular reflection of light when light is incident on the still water and irregular reflection of light when light is incident on the water as ripples are produced on its surface when a stone is thrown in the water.
Still water behaves as a plane and smooth surface while oscillating water behaves as a rough surface.
In simple words: Still water shows regular reflection because it's smooth, but rippling water causes irregular reflection due to its rough, disturbed surface.

🎯 Exam Tip: Use practical examples, like still versus rippled water, to illustrate the real-world differences between regular and irregular reflection and their visual effects.

 

Question iii. Are the laws of reflection followed in these types of reflection?
Answer: Yes.
In simple words: The laws of reflection, stating that the angle of incidence equals the angle of reflection, apply at every point of reflection, whether the surface is smooth or rough.

🎯 Exam Tip: Remember that the laws of reflection hold true for both regular and irregular reflections, as they apply to each individual ray at its point of incidence.

 

7. Solve The Following Examples.

 

Question a. If the angle between the plane mirror and the incident ray is \(40^\circ\), what are the angles of incidence and reflection?
Solution: The angle between the plane mirror and the incident ray is \(40^\circ\). Therefore, the angle of incidence \( (i) \) = the angle made by the incident ray with the normal to the plane mirror = \(90^\circ - 40^\circ = 50^\circ\). The angle of reflection, \( r = i = 50^\circ \).
In simple words: The angle of incidence is measured from the normal, not the mirror surface, and for any reflection, the angle of incidence always equals the angle of reflection.

🎯 Exam Tip: Always measure angles of incidence and reflection with respect to the normal (perpendicular to the surface), not the surface itself, to avoid common errors in calculations.

 

Question b. If the angle between the mirror and reflected ray is \(23^\circ\), what is the angle of incidence of the incident ray?
Solution: The angle between the mirror and the reflected ray is \(23^\circ\). Therefore, the angle of reflection \( (r) \) = the angle made by the reflected ray with the normal to the plane mirror = \(90^\circ - 23^\circ = 67^\circ\).
\( \therefore \) The angle of incidence, \( i = r = 67^\circ \).
In simple words: Since the angle of reflection is \(67^\circ\) when measured from the normal, the angle of incidence must also be \(67^\circ\) due to the laws of reflection.

🎯 Exam Tip: Practice converting angles given relative to the mirror surface into angles relative to the normal, as this is a frequent step in solving reflection problems.

 

Project:

 

Question a. Apollo astronauts who stepped on the moon have kept some large mirrors there. Collect information about how the distance to the moon is measured using these.
Answer: Students are encouraged to research and collect information on this topic.
In simple words: Lasers are aimed at mirrors left on the Moon, and by measuring the time it takes for the light to return, scientists can precisely calculate the Earth-Moon distance.

🎯 Exam Tip: For project-based questions, focus on gathering reliable information from scientific sources to understand the underlying principles and practical applications.

 

Class 8 Science Chapter 16 Reflection Of Light Important Questions And Answers

Rewrite The Following Statements By Selecting The Correct Option:

 

Question 1. If the angle made by the incident ray with the surface of a plane mirror is \(30^\circ\), the angle of reflection must be ........ .
(a) \(30^\circ\)
(b) \(90^\circ\)
(c) \(60^\circ\)
(d) \(15^\circ\)
Answer: (c) \(60^\circ\)
If the angle made by the incident ray with the surface of a plane mirror is \(30^\circ\), the angle of incidence (with the normal) is \(90^\circ - 30^\circ = 60^\circ\). According to the law of reflection, the angle of reflection must also be \(60^\circ\).
In simple words: The angle of incidence is calculated from the normal, so if the angle with the mirror is \(30^\circ\), the angle of incidence is \(60^\circ\), and thus the angle of reflection is also \(60^\circ\).

🎯 Exam Tip: Always remember that angles of incidence and reflection are measured relative to the normal, not the mirror surface. A common mistake is using the angle with the surface directly.

 

Question 2. If the angle of incidence is \(40^\circ\), the angle made by the reflected ray with the surface of the plane mirror must be ....... .
(a) \(40^\circ\)
(b) \(50^\circ\)
(c) \(20^\circ\)
(d) \(80^\circ\)
Answer: (b) \(50^\circ\)
If the angle of incidence is \(40^\circ\), then the angle of reflection is also \(40^\circ\). The angle made by the reflected ray with the surface of the plane mirror is \(90^\circ - 40^\circ = 50^\circ\).
In simple words: If the angle of reflection from the normal is \(40^\circ\), then the angle formed between the reflected ray and the mirror's surface is found by subtracting this from \(90^\circ\).

🎯 Exam Tip: Be precise in identifying whether the question asks for the angle of incidence/reflection (with normal) or the angle with the mirror surface. Convert between them using \(90^\circ\).

 

Question 3. If the angle of incidence is \(20^\circ\), the angle made by the reflected ray with the normal to the surface must be ..........
(a) \(20^\circ\)
(b) \(70^\circ\)
(c) \(10^\circ\)
(d) \(40^\circ\)
Answer: (a) \(20^\circ\)
If the angle of incidence is \(20^\circ\), the angle made by the reflected ray with the normal to the surface must be \(20^\circ\). (According to the law of reflection, angle of incidence = angle of reflection).
In simple words: According to the law of reflection, the angle at which light bounces off a surface is exactly equal to the angle at which it hits, both measured from the normal.

🎯 Exam Tip: The first law of reflection (angle of incidence = angle of reflection) is fundamental; ensure you can apply it directly to simple scenarios.

 

Question 4. In a kaleidoscope, the mirrors are inclined to each other at ........
(a) \(60^\circ\)
(b) \(30^\circ\)
(c) \(45^\circ\)
(d) \(90^\circ\)
Answer: (a) \(60^\circ\)
In a kaleidoscope, the mirrors are inclined to each other at \(60^\circ\).
In simple words: Kaleidoscopes often use three mirrors set at \(60^\circ\) to each other to create many symmetrical reflections.

🎯 Exam Tip: Memorize the typical mirror angles used in common optical instruments like the kaleidoscope, as these are often direct recall questions.

 

Question 5. In a periscope, the mirrors are ........
(a) parallel to each other
(b) at right angles to each other
(c) inclined at \(45^\circ\) to each other
(d) inclined at \(60^\circ\) to each other
Answer: (a) parallel to each other
In a periscope, the mirrors are parallel to each other.
In simple words: A periscope uses two parallel mirrors to allow viewing of objects that are not in the direct line of sight.

🎯 Exam Tip: Understand the mirror arrangement in a periscope (parallel and at \(45^\circ\) to the incident light) and how it enables viewing around obstacles.

 

Find The Odd One Out And Give The Reason:

 

Question 1. Plane mirror, Plywood, Wood, Rough tile.
Answer: Plane mirror. In this case, regular reflection of light takes place. In other cases, reflection of light is irregular.
In simple words: A plane mirror creates clear, regular reflections, while plywood, wood, and rough tile cause light to scatter irregularly.

🎯 Exam Tip: When identifying the odd one out, focus on the distinct physical property or behavior that differentiates one item from the others in the given category.

 

State Whether The Following Statements Are True Or False. (If A Statement Is False, Correct It And Rewrite It.)

 

Question 1. The sense of vision is the most important among our five senses.
Answer: True.
In simple words: Vision is widely considered the most dominant sense for humans, providing the majority of information about our environment.

🎯 Exam Tip: For true/false questions, assess the statement's accuracy based on general scientific understanding; if false, provide the correct information clearly.

 

Question 2. In a periscope, the angle between the incident ray and the normal to the mirror is \(30^\circ\).
Answer: False. (In a periscope, the angle between the incident ray and the normal to the mirror is \(45^\circ\).)
In simple words: Periscopes are designed so that light rays hit the mirrors at a \(45^\circ\) angle to the normal, ensuring efficient redirection of the light.

🎯 Exam Tip: Memorize specific angles related to optical instruments; periscopes typically use mirrors placed at \(45^\circ\) to redirect light by \(90^\circ\).

 

Answer The Following Questions In One Sentence Each:

 

Question 1. What is an incident ray? OR Define incident ray.
Answer: A ray of light falling on a surface is called an incident ray.
In simple words: An incident ray is the path of light traveling towards a surface.

🎯 Exam Tip: Know the basic definitions in optics, as they form the foundation for understanding more complex concepts.

 

Question 2. What is the point of incidence? OR Define point of incidence.
Answer: The point at which the incident ray strikes the surface is called the point of incidence. [Note: It is also the point of reflection.]
In simple words: The point of incidence is the exact spot where a light ray hits a surface.

🎯 Exam Tip: Visualizing the point of incidence helps in correctly drawing normals and measuring angles in ray diagrams.

 

Question 3. What is the normal? OR Define normal.
Answer: The perpendicular to a surface at the point of incidence is called the normal.
In simple words: The normal is an imaginary line perpendicular to a surface at the point where light strikes it.

🎯 Exam Tip: The normal is a critical reference line for all reflection and refraction angle measurements; always draw it first in ray diagrams.

 

Question 4. What is the reflected ray? OR Define reflected ray.
Answer: The ray of light that leaves the surface at the point of reflection (the same as the point of incidence) is called the reflected ray.
In simple words: A reflected ray is the light that bounces off a surface after striking it.

🎯 Exam Tip: Distinguish clearly between the incident ray (approaching) and the reflected ray (leaving) the surface.

 

Question 5. What is the angle of incidence? OR Define angle of incidence.
Answer: The angle between the incident ray and the normal is called the angle of incidence.
In simple words: The angle of incidence is the angle between the incoming light ray and the normal line to the surface.

🎯 Exam Tip: Always measure the angle of incidence from the normal, not the surface, for accurate calculations in optics problems.

 

Question 6. What is the angle of reflection? OR Define angle of reflection.
Answer: The angle between the reflected ray and the normal is called the angle of reflection.
In simple words: The angle of reflection is the angle between the outgoing light ray and the normal line to the surface.

🎯 Exam Tip: Ensure consistency: if the angle of incidence is measured from the normal, the angle of reflection must also be measured from the normal.

 

Try This:

Switch off the light in your room at night for some time and then turn it on again.

 

Question 1. Could you see the objects in the room clearly when the light was switched off?
Ans. No.
In simple words: Without light, objects cannot reflect any illumination, making them invisible to our eyes.

🎯 Exam Tip: Use simple observations like this to explain the fundamental role of light in the process of vision.

 

Question 2. What did you feel when it was turned on again?
Answer: We could see the objects clearly. From the above activity you can notice that there is some connection between the sense of vision and light. When we switch off the light at night, the objects in the room cannot be seen and they can be seen as before when the light is switched on again. Thus, we can see objects when the light coming from these objects enters our eyes.
In simple words: When the light turns on, objects become visible again because they reflect light, which then enters our eyes, allowing us to perceive them.

🎯 Exam Tip: This activity demonstrates that light reflecting off objects and entering our eyes is the essential mechanism for sight.

 

Answer The Following Questions:

 

Question 1. What is reflection of light?
Answer: When light rays fall on an object, their direction changes and they turn back. This is called the reflection of light.
In simple words: Reflection of light is when light bounces off a surface and changes direction.

🎯 Exam Tip: A clear, concise definition of reflection is fundamental; ensure you can explain it in your own words.

 

Try This:

Material:

Torch light, mirror, a stand for hanging the mirror, black paper, comb, white paper, drawing board.

Activity:

(1) Fit a white paper tightly over a table or drawing board.
(2) Leaving out some portion in the middle of the comb, cover the rest with black paper so that light can only pass through the open central portion.
(3) Hold the comb perpendicular to the white paper and throw torch light on its central portion.
(4) Adjust the comb and torch so as to get light rays on the white paper. Now keep a mirror in the path of this ray of light as shown in the figure.
(5) What do you observe?
ℹ️ चित्र व्याख्या (Diagram Explanation): इस चित्र में एक टॉर्च से निकली प्रकाश किरण को एक कंघी के खुले हिस्से से गुज़रते हुए दिखाया गया है, जिससे प्रकाश की एक सीधी किरण बनती है। यह प्रकाश किरण फिर एक दर्पण पर पड़ती है और उससे परावर्तित होकर एक नई दिशा में चली जाती है। यह सेटअप प्रकाश के परावर्तन को प्रदर्शित करता है।
Answer: Light rays which fall on the mirror get reflected and travel in a different direction.
In simple words: Light travels in a straight line, but when it hits a mirror, it bounces off and changes its path.

🎯 Exam Tip: Practical activities help to solidify theoretical concepts; understand how this experiment demonstrates the change in direction of light upon reflection.

 

Question 2. State the laws of reflection of light.
Answer:
(1) The angle of reflection is equal to the angle of incidence.
(2) The incident ray, the reflected ray and the normal lie in the same plane.
(3) The incident ray and the reflected ray are on the opposite sides of the normal.
In simple words: The laws of reflection state that light bounces off at the same angle it hits, and the incoming ray, outgoing ray, and the perpendicular line all lie in the same flat plane.

🎯 Exam Tip: Accurately stating all three laws of reflection is crucial; pay attention to details like "same plane" and "opposite sides of the normal."

 

Try This:

Verification of the laws of reflection of light.

Equipment:

Mirror, drawing board, pins, white paper, protractor, scale, pencil.

Activity:

(1) Fit a white paper on the drawing board tightly as possible.
(2) On the paper draw a line PQ indicating the position of the mirror.
(3) Draw a perpendicular ON to PQ at point O.
(4) Draw a ray AO making an angle of \(30^\circ\) with ON.
(5) Fix two pins S and R along AO.
(6) Fix the mirror to a stand and place it along PQ perpendicular to the drawing board.
(7) Fix pins at T and U along the line joining the bottom of the reflected images of the pins at S and R.
(8) Remove the mirror and join the points T and U and extend it up to O.
(9) Measure \( \angle TON \).
(10) Repeat steps 4 to 9 for angle of incidence equal to \(45^\circ\) and \(60^\circ\) and write down the angles in the following table.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र प्रकाश के परावर्तन के नियमों को सत्यापित करने के लिए एक प्रायोगिक व्यवस्था को दर्शाता है। एक समतल दर्पण \(PQ\) पर बिंदु \(O\) पर एक अभिलंब \(ON\) खींचा गया है। एक आपतित किरण \(AO\) को दो पिन \(S\) और \(R\) द्वारा दर्शाया गया है, जिसका आपतन कोण \(30^\circ\) है। परावर्तित किरण को दो पिन \(T\) और \(U\) की छवियों के माध्यम से देखा जाता है, जो आँख से देखने पर एक सीधी रेखा में दिखाई देते हैं।

S.No.	Angle of incidence \((\angle i)\)	Angle of reflection \((\angle r)\)
1.	\(30^\circ\)
2.	\(45^\circ\)
3.	\(60^\circ\)

What relation do you find between the angle of incidence and the angle of reflection? If you have done the experiment carefully, you will find that the angle of incidence is equal to the angle of reflection in all three cases. This verifies the laws of reflection.
In simple words: This experiment shows that the angle at which light hits a mirror is always the same as the angle at which it bounces off, proving the law of reflection.

🎯 Exam Tip: When conducting experiments, precise measurements are key. In reflection, confirm that \( \angle i = \angle r \) for different angles to verify the law.

 

Question a. What will happen when a light ray is incident perpendicular to the mirror?
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र दर्शाता है कि जब एक प्रकाश किरण एक दर्पण की सतह पर लंबवत (यानी \(90^\circ\) पर) आपतित होती है, तो वह उसी पथ पर वापस परावर्तित हो जाती है। आपतित किरण और परावर्तित किरण एक ही सीधी रेखा में होती हैं।
Here, \( r = i = 90^\circ \). Hence the light ray, on reflection, will retrace the path.
In simple words: If light hits a mirror straight on, at a \(90^\circ\) angle to the surface, it reflects directly back along the same path.

🎯 Exam Tip: Remember this special case: perpendicular incidence means the light ray reflects back along its original path, as both angle of incidence and reflection are \(0^\circ\) with respect to the normal (which coincides with the ray).

 

Question 3. Figures (a) and (b) show three parallel rays, shown in grey, incident on smooth and rough surfaces. The reflected rays drawn using laws of reflection are shown in red. 1. Rays reflected from which surface are parallel to one another? 2. What conclusion can you draw from the figure?
Answer: 1. Rays reflected from the smooth surface are parallel to one another.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र दो प्रकार के प्रकाश परावर्तन को दर्शाता है। ऊपर वाला चित्र (a) एक चिकनी सतह से नियमित परावर्तन दिखाता है, जहाँ समानांतर आपतित किरणें समानांतर परावर्तित होती हैं। नीचे वाला चित्र (b) एक खुरदरी सतह से अनियमित परावर्तन दिखाता है, जहाँ समानांतर आपतित किरणें विभिन्न दिशाओं में परावर्तित होती हैं। दोनों में आपतन कोण (i) और परावर्तन कोण (r) को दर्शाया गया है।

Question 4. What is regular reflection of light?
Answer: The reflection of light from a plane and smooth surface is called regular reflection of light.
In simple words: Regular reflection happens when light hits a very smooth surface, like a mirror, and all the light rays bounce off in the same organized direction.

🎯 Exam Tip: Understanding the surface properties (smooth vs. rough) is key to differentiating reflection types for high scores.

Question 5. What is irregular reflection of light?
Answer: The reflection of light from a rough surface is called irregular reflection of light.
In simple words: Irregular reflection occurs when light hits a rough surface, causing the light rays to scatter in many different directions.

🎯 Exam Tip: Focus on how the surface texture influences the direction of reflected light rays for a comprehensive answer.

Question 1. How do you see if the barber m a saloon has cut the hair on your neck properly or not?
Answer: In a saloon, there are mirrors in your front and at back. The image of the back of your head is formed in the mirror at the back. The image of this image is formed in the mirror in front of you. Thus you can see how the hair at the backside of your head is cut.
In simple words: You see the back of your head by using two mirrors: one behind you reflects your head, and another in front reflects that image, bringing it into your view.

🎯 Exam Tip: This question assesses understanding of multiple reflections; clearly describe the path of light and images formed.

Question 2. What type of image do we see in a mirror? What happens to the left and right sides?
Answer: The image in a plane mirror is upright (erect) and of the same size as the object, but the left and right sides are interchanged. Our right hand appears to be the left hand in the image and the left hand appears to be the right hand in the image. (This is called lateral inversion.)
In simple words: A plane mirror shows an image that is the same size and upright as the object, but it flips the left and right sides, a phenomenon called lateral inversion.

🎯 Exam Tip: Remember to include "upright," "same size," and "lateral inversion" when describing plane mirror images for full marks.

Question 3. How do we see the image of the moon in water?
Answer: The moon is not self luminous. The sunlight falling on the surface of the moon is reflected. This reflected light is again reflected by water to give us the image of the moon.
In simple words: We see the moon's image in water because moonlight (sunlight reflected by the moon) bounces off the water's surface and enters our eyes.

🎯 Exam Tip: Emphasize that the moon reflects sunlight and that water acts as a secondary reflector for a complete explanation.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक बहुरूपदर्शक (kaleidoscope) की आंतरिक संरचना को दर्शाता है, जिसमें एक कार्डबोर्ड ट्यूब के अंदर समानांतर क्रम में रखे गए दर्पण होते हैं। इसमें देखने के लिए एक सिरा (see through this) और एक बंद करने वाली टोपी (cap for closing) होती है, जिससे प्रकाश के बहु-परावर्तन से सुंदर पैटर्न बनते हैं।
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक साधारण पेरिस्कोप की कार्यप्रणाली को दर्शाता है। इसमें दो दर्पण 45 डिग्री के कोण पर रखे होते हैं, जिससे प्रकाश की किरणें मुड़कर प्रेक्षक की आँख तक पहुँचती हैं। यह वस्तुओं को ऊपर या बाधा के पार देखने में मदद करता है।
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक पनडुब्बी पर लगे पेरिस्कोप को दिखाता है। पेरिस्कोप का उपयोग पनडुब्बी के अंदर से पानी की सतह के ऊपर की वस्तुओं को देखने के लिए किया जाता है, जिससे यह पानी के नीचे रहते हुए भी आसपास का निरीक्षण कर पाती है।

Example Questions For Practice

Question 1. If the angle between the plane mirror and the incident ray is 20°, what is the angle between the reflected ray and the plane mirror?
Answer: 20°.
In simple words: If the incident ray makes a 20° angle with the mirror, the reflected ray will also make a 20° angle with the mirror, according to the laws of reflection.

🎯 Exam Tip: Remember that the angle of incidence with the surface is equal to the angle of reflection with the surface, not the normal.

Question 2. See Fig. In terms of O, what are the angles (i) AON (ii) BON (iii) AOB (iv) BOQ?
Answer:
(i) 90° - \( \theta \)
(ii) 90° - \( \theta \)
(iii) 180° - 2\( \theta \)
(iv) 90° - \( \theta \)
In simple words: Using the diagram where \( \theta \) is the angle between the incident ray and the mirror, angles AON, BON, and BOQ are \( 90^\circ - \theta \), while AOB, which is the total angle between the incident and reflected rays, is \( 180^\circ - 2\theta \).

🎯 Exam Tip: Clearly define what each angle represents (e.g., angle of incidence, angle of reflection, angle with mirror surface) to correctly calculate these values based on the laws of reflection.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक समतल दर्पण पर प्रकाश के परावर्तन को दर्शाता है। इसमें एक आपतित किरण (A) दर्पण से टकराकर परावर्तित किरण (B) के रूप में वापस लौटती है। N सामान्य रेखा है और \( \theta \) आपतित किरण और सामान्य रेखा के बीच का कोण है।