Class 7 Science Chapter 4 – Fun with Light: Shadow and Reflection – All Textual Solutions | ASSEB Assam (English Medium)

Class 7 Science Chapter 4 Fun with Light: Shadow and Reflection Solutions | ASSEB Assam | English Medium

Class 7 Science (Amar Bijan) Chapter 4 – Fun with Light: Shadow and Reflection Complete Textual Question Answers and Solutions (ASSEB Assam – English Medium)

The fourth chapter of the Class 7 Science (English Medium) syllabus, ‘Fun with Light: Shadow and Reflection,’ is an exciting and visually engaging topic in physics. Based on the new ASSEB (Assam State School Education Board) guidelines and the latest National Education Policy (NEP) framework according to the current syllabus, we have prepared comprehensive textual question answers for this chapter. This special guide includes very short answers (VSA), short questions, long descriptive answers, multiple-choice questions (MCQs), and additional questions. Brought to you by Ospin Academy, these solutions are accurate, easy to understand, and highly exam-oriented.

In ‘Fun with Light: Shadow and Reflection’, students explore the intriguing behavior of light, including its rectilinear propagation (traveling in straight lines), the formation of shadows by opaque objects, the working of a pinhole camera, and the principles of reflection from mirrors. Understanding these basic optical phenomena is crucial for exam preparation. Our textual solutions not only cover the textbook exercises but also provide extra important questions and MCQs to ensure students have a thorough grasp of the topic.

What you will learn and get from these textual solutions:

• Clear explanations distinguishing between transparent, translucent, and opaque objects.
• 1-mark objective questions (VSA), MCQs, and detailed 2-3 mark short questions tailored for exams.
• Step-by-step explanations for 4-5 mark long questions, including the setup of a pinhole camera and the laws of reflection.
• A wide range of additional questions and MCQs specifically designed according to the new syllabus pattern.
• Comprehensive insights into everyday optical illusions and shadow formation, explained in simple English.

Special Features of Ospin Academy’s Notes:

• Prepared strictly according to the new ASSEB syllabus and current educational guidelines.
• 100% accurate and written in simple, easy-to-memorize English (Class 7 Science Notes).
• Includes quick revision pointers on light and mirrors, highly beneficial for last-minute exam preparation.
• Exclusive compilation of extra important questions and MCQs to maximize your scores.

Aiming for academic excellence, Ospin Academy provides these comprehensive textual solutions to aid students in their studies. Start your preparation today and secure the highest marks in Class 7 Science.

 SCERT Assam, Class 7: Science

Lesson-4                                                                                   Ospin Academy

Fun with Light: Shadow and Reflection

 

EXERCISE

1. Darken the circle of correct answer.

(i) Which of the following is an artificial source of light?
(a) Sun
(b) Firefly
(c) Jelly fish
(d) Electric bulb
Answer: (d)

(ii) Which of the following is not essential for formation of a shadow?
(a) Screen
(b) Object
(c) Colour of the object
(d) Source of light
Answer: (c)

(iii) The colour of a shadow is-
(a) Always black and white
(b) Only black
(c) Only white
(d) Same as that of the object
Answer: (b)

(iv) Which of these materials can we see through?
(a) A piece of iron
(b) A piece of wood
(c) A glass tumbler
(d) A thick book
Answer: (c)

(v) Sima is 3m away from a plane mirror. If she moves few steps closer to the mirror, what change will happen to the size or the images in the mirror?
(a) Will decrease
(b) Will increase
(c) Will be same
(d) Will be inverted
Answer: (c)

2. Fill in the blanks.
(i) A shadow has no __________.
Answer: colour

(ii) Pinhole camera forms __________ image.
Answer: inverted 

(iii) Rubber is __________ but glass is __________.
Answer: opaque, transparent 

(iv) When we look in a plan mirror, left hand of our body looks like right hand. This phenomenon is called __________.
Answer: lateral inversion 

3. Write True of False
(i) Non luminous objects emit the light of their own.
Answer: False 

(ii) Light travels in the form of rectilinear propagation.
Answer: True 

(iii) Periscope is based on the principle of reflection of light.
Answer: True 

(iv) Moon is luminous object.
Answer: False 

4. Match the following : 

Part A	Part B
(i) A body that allows light to pass through it.	(i) Luminous object
(ii) Moon	(ii) Reflection
(iii) A body emitting its own light.	(iii) Transparent object
(iv) Bouncing back of light from a surface.	(iv) Non-luminous object

Answer:

Part A	Part B
(i) A body that allows light to pass through it.	(iii) Transparent object
(ii) Moon	(iv) Non-luminous object
(iii) A body emitting its own light.	(i) Luminous object
(iv) Bouncing back of light from a surface.	(ii) Reflection

5. Think and Answer.
(i) Can an object have more than one shadow?

Answer: Yes, this happenes when there are more than one source of light around the object.

(ii) What are the conditions needed for a shadow to be formed?

Answer: The conditions are a source of light, an opaque object and a screen. 

(iii) Can we see a shadow if there is no source of light?

Answer: No, we cannot see a shadow if there is no source of light. 

(iv) Suppose you have a red bulb and a blue bulb. If you switch on both the bulbs and place an object in front of the red bulb, what would be the colour of the shadow? If you place the object in front of the blue bulb what colour would the shadow be?

Answer: In both the cases, colour of the shadow would be black. (v) Why the word ‘AMBULANCE’ is written inverted in front of an ambulance? 

Answer: In a mirror, the left side of the object appears as the right side of the image and the right side of the object appears as the left side of the image, which is called lateral inversion. So, when the word ‘AMBULANCE’ is written in inverted manner in front of an ambulance, a driver of a vehicle in front of the ambulance can read the word in correct order in the rear-view mirror. 

(vi) Moon appears to be bright at night. Does it mean that it is luminous object?

(vi) Moon appears to be bright at night. Does it mean that it is luminous object?
Answer: No, the moon is categorized as a non-luminous body. It does not generate its own light; rather, it appears luminous to us because its surface reflects the light emitted by the sun towards the Earth. 

(vii) Suppose you are in a dark room, will you see the things available in the room? Will you able to see the things outside the room if there is light outside?
Answer: While inside a completely dark room, I will be unable to see the objects within it due to the absence of light reflecting off them into my eyes. However, I will be able to clearly see objects located outside the room, provided they are illuminated by an external light source.

(viii) Why we can’t see the shadow of a flying aeroplane?

Answer: We can not see the shadow of a flying aeroplane, because the distance between it and the earth’s surface is very large. In such situation the central dark part of the shadow becomes too small and the surrounding light dark part spreads and becomes faint.

(ix) What is the principle of a pinhole camera? What are the characteristics of an image formed by a pinhole camera? 

Answer: The principle of a pinhole camera is that light travels in a straight line. The characterisitics of an image formed by a pinhole camera are (a) It is inverted, (b) We can touch the image with our hands.

(x) Mina is standing in front of a plane mirror at a distance of 6m. She moves forward by 1m towards the mirror. What is the distance between Mina and the image?

Answer: Distance between Mina and the image is 10m. (xi) Classify the following objects or materials as opaque, transparent or translucent, luminous or non luminous. Mirror, a piece of wood, foggy glass, a piece of rock, Sun, Moon, tube light, a CD, a sheet of aluminium, firefly.

Answer: Opaque: a piece of wood, piece of rock, tube light, a CD, a sheet Of aluminimum, firefly, Sun, Moon, mirror.
Translucent : Foggy glass.
Luminous : Sun , tube light , firefly .
Non-luminous : Mirror , a piece of wood , foggy glass , a piece of rock , Moon a CD , a sheet of aluminium 

Multiple Choice Questions (MCQs)

1. Light is a form of:
(A) Matter
(B) Energy
(C) Mass
(D) Fluid
Answer: (B)

2. Objects that emit their own light are known as:
(A) Transparent objects
(B) Opaque objects
(C) Luminous objects
(D) Non-luminous objects
Answer: (C)

3. Which of the following allows light to pass through it completely?
(A) Wood
(B) Clear water
(C) Iron sheet
(D) Tracing paper
Answer: (B)

4. A shadow is formed because light travels in a:
(A) Zigzag path
(B) Circular path
(C) Straight line
(D) Random motion
Answer: (C)

5. Tracing paper is an example of a:
(A) Transparent object
(B) Translucent object
(C) Opaque object
(D) Luminous object
Answer: (B)

6. What happens when light falls on a highly polished surface like a mirror?
(A) It gets absorbed
(B) It passes through
(C) It scatters in all directions
(D) It gets reflected regularly
Answer: (D)

7. The image formed by a plane mirror is always:
(A) Inverted
(B) Smaller than the object
(C) Laterally inverted
(D) Real and can be caught on a screen
Answer: (C)

8. Which of the following is a non-luminous object?
(A) A glowing tube light
(B) The Sun
(C) A wooden chair
(D) A lighted candle
Answer: (C)

9. In a pinhole camera, the image obtained is:
(A) Erect and real
(B) Erect and virtual
(C) Inverted and real
(D) Inverted and virtual
Answer: (C)

10. Shadows are longest during:
(A) Early morning and late evening
(B) Exactly at noon
(C) Midnight
(D) 10 AM
Answer: (A)

11. The dark inner region of a shadow where no light reaches is called:
(A) Penumbra
(B) Umbra
(C) Reflection
(D) Silhouette
Answer: (B)

12. What property of a mirror allows us to see our image?
(A) Refraction
(B) Dispersion
(C) Reflection
(D) Absorption
Answer: (C)

13. If you stand 2 meters in front of a plane mirror, what is the distance between you and your image? তোমাৰ প্ৰতিবিম্বৰ মাজৰ দূৰত্ব কিমান হ’ব?)
(A) 2 meters
(B) 4 meters
(C) 1 meter
(D) 8 meters
Answer: (B)

14. An object placed between a light source and a screen must be ________ to form a clear shadow.
(A) Transparent
(B) Translucent
(C) Opaque
(D) Gaseous
Answer: (C)

15. The phenomenon where light bounces back into the same medium after hitting a surface is termed:
(A) Shadowing
(B) Reflection
(C) Inversion
(D) Transmission
Answer: (B)

16. Which natural phenomenon proves that light travels in straight lines?
(A) Formation of rainbows
(B) Twinkling of stars
(C) Formation of shadows
(D) Blue colour of the sky
Answer: (C)

17. A glass window with a thick layer of condensed water droplets acts as a:
(A) Luminous body
(B) Transparent body
(C) Translucent body
(D) Opaque body
Answer: (C)

18. The size of the shadow depends on the:
(A) Distance between the light source and the object
(B) Colour of the object
(C) Brightness of the room
(D) Speed of light
Answer: (A)

19. When the distance between the object and the screen is increased, the shadow:
(A) Becomes smaller
(B) Becomes larger and less distinct
(C) Disappears completely
(D) Changes its colour
Answer: (B)

20. Which of the following is NOT a source of light?
(A) A star
(B) A burning matchstick
(C) A mirror reflecting sunlight
(D) A flashlight
Answer: (C)

Long Questions with Answers

1. Explain the difference between transparent, translucent, and opaque objects with two examples of each.
Answer: Transparent objects allow light to pass through them completely, allowing us to see clearly through them. Examples are clean glass and clear water. Translucent objects allow only a partial amount of light to pass, so objects on the other side appear blurred or fuzzy. Examples include butter paper and frosted glass. Opaque objects completely block light, casting dark shadows and preventing us from seeing through them at all. Examples are wood and iron.

2. How is a shadow formed? Detail the three primary requirements for the formation of a shadow.
Answer: A shadow is formed when light travelling in a straight path is obstructed. When an opaque object is placed in the path of light, it blocks the rays, creating a dark, unlit area behind it known as a shadow. The three primary requirements are: 1) A luminous light source (like the Sun or a lamp) to emit light. 2) An opaque object to block the light. 3) A screen or a solid surface (like a wall or the ground) where the shadow can fall and be seen.

3. What is lateral inversion? Explain how it affects the image formed in a plane mirror.
Answer: Lateral inversion is an optical phenomenon associated with plane mirrors where the left side of a real object appears as the right side of its virtual image, and vice versa. For example, if you raise your left hand in front of a mirror, your mirror image appears to raise its right hand. This inversion happens because light rays reflect directly straight back from the flat surface of the mirror, reversing the image horizontally but keeping it erect vertically.

4. Describe the construction and working principle of a pinhole camera.
Answer: A pinhole camera is a simple light-proof box with a tiny, pin-sized hole punctured on one face and a translucent screen (like tracing paper) fixed on the opposite face. It operates on the principle that light travels in straight lines. Light rays coming from the top of an object pass through the tiny hole and strike the bottom of the screen, while rays from the bottom of the object strike the top of the screen. This crossing of straight light rays through the small aperture results in an inverted (upside down) image of the object on the screen.

5. Why does the size of a shadow change throughout the day?
Answer: The size of a shadow cast by sunlight changes constantly throughout the day due to the varying angle and apparent position of the Sun in the sky relative to the object. In the early morning and late afternoon, the Sun is low on the horizon, causing its light rays to strike objects at a steep, slanting angle, resulting in very long shadows. At noon, when the Sun is positioned almost directly overhead, the light rays shine straight down, creating the shortest possible shadow situated right beneath the object.

6. Explain the difference between an image formed by a plane mirror and a shadow.
Answer: A mirror image is formed by the reflection of light from a polished surface. It is highly detailed, shows all the exact colours of the object, undergoes lateral inversion, and gives a sense of depth or 3D appearance. In contrast, a shadow is simply a dark area created when an opaque object blocks light. A shadow is always black or dark grey regardless of the object’s colour, shows no surface details, appears entirely flat (2D), and its size can change drastically depending on the light source’s distance.

7. How does a periscope work, and where is it commonly used?
Answer: A periscope is an optical instrument that allows observation over, around, or through an obstacle. It consists of a long tube with two plane mirrors placed at opposite ends, both set parallel to each other at a precise 45-degree angle. Light entering the top mirror reflects downward at a 90-degree angle to the bottom mirror, which then reflects it another 90 degrees directly into the viewer’s eye. Periscopes are most famously used in submarines to view objects above the water’s surface while remaining safely submerged.

8. Can a transparent object form a shadow? Give reasons for your answer.
Answer: A perfectly transparent object generally does not form a distinct, dark shadow. Because its molecular structure allows almost all light rays to pass completely through it without being absorbed or blocked, it fails to create the dark unlit region required for a shadow. However, in reality, no physical object is 100% transparent. Even a clear glass might block or slightly bend (refract) a tiny fraction of light, potentially creating an extremely faint, almost imperceptible shadow, but it will never form a dark umbra like an opaque object.

9. Discuss how the distance between the light source and the opaque object affects the size and sharpness of a shadow.
Answer: The position of the light source drastically alters the shadow. When a light source is moved closer to an opaque object, the object blocks a wider angle of the diverging light rays, causing the shadow projected on the screen to become much larger and often fuzzier at the edges (a larger penumbra). Conversely, when the light source is moved further away from the object, the light rays become more parallel. This results in a smaller, sharper, and much more clearly defined shadow on the screen.

10. Explain the phenomenon of reflection of light and state the condition required for a clear reflection.
Answer: Reflection of light is the optical process where light rays hitting a surface bounce back into the original medium rather than passing through it or being absorbed. This is similar to a rubber ball bouncing off a hard wall. For a clear, distinct image reflection to occur (regular reflection), the reflecting surface must be extremely smooth, flat, and highly polished, like a plane mirror or still water. Rough or uneven surfaces scatter the light rays in multiple directions (diffuse reflection), which illuminates the object but fails to form a coherent image.