RBSE Solutions for Class 7 Science Chapter 15 Light

Rajasthan Board RBSE Solutions for Class 7 Science Chapter 15 Light Textbook Exercise Questions and Answers.

RBSE Class 7 Science Solutions Chapter 15 Light

RBSE Class 7 Science Light InText Questions and Answers

Page 176

Question 1. 
Paheli wants to know, what makes things visible to us?
Answer:
Things are visible to us because of the reflection of light.

Page 177

Question 2. 
Boojho noted in his notebook: Is it not surprising that my image is of the same size as me whether the mirror is small or large?
Answer:
Yes, image formed by the plane mirror is of the same size as the object. A plane mirror has plane reflecting surface without any curve.

Page 178

Question 3. 
Boojho saw an ambulance on the road. He was surprised to see that the word ‘AMBULANCE’ in front was written in a strange manner.
Answer:
The image found on rear view mirror of the vehicle is laterally inverted i.e., right appears left and left appears right. So, when the driver of vehicle ahead of an ambulance looks in his/her rear view mirror, he/she can read the strange word as written on it.

Page 186

Question 4. 
Prism splits the light. Does this mean that the white light consists of seven colours?
Answer:
Yes, white light consists of seven colours - red, orange, yellow, green, blue, indigo and violet. Prism splits a beam of sunlight into seven colours.

RBSE Class 7 Science Light Textbook Questions and Answers

Question 1. 
Fill in the blanks 
(a) An image that cannot be obtained on a screen is called ...............................
(b) Image formed by a convex ............................... is always virtual and smaller in size.
(c) An image formed by a    ............................... mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a ............................... image.
(e) An image formed by a concave ............................... cannot be obtained on a screen.
Answer:
(a) virtual image 
(b) mirror 
(c) plane 
(d) real 
(e) lens.

Question 2. 
Mark ‘T’ if the statement is true and 'F' if it is false:
(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)
(b) A concave lens always form a virtual image. (T/F)
(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F)
(d) A real image cannot be obtained on a screen. (T/F)
(e) A concave mirror always form a real image. (T/F)
Answer:
(a) False 
(b) True 
(c) True 
(d) False 
(e) False.

Question 3. 
Match the items given in Column I with one or more items of Column II: 

Answer:

Question 4. 
State the characteristics of the image formed by a plane mirror.
Answer:
The image formed by a plane mirror has the following characteristics:

• The distance of the object in front of the mirror is same as the distance of the image behind the mirror. 
• The image formed by a plane mirror is virtual and erect.
• The size of the image is equal to the object size.
• The image formed by plane mirror is laterally inverted.

Question 5. 
Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings. 
Answer:
The letters of English alphabet which give exactly same image in the plane mirror like the letter itself are:
A, H, I, M, O, T, U, V, W, X, Y 

Question 6. 
What is a virtual image? Give one situation where a virtual image is formed.
Answer:
Virtual image is the image which cannot be touched and cannot be obtained on screen. Eg. the image formed by the plane mirror is a virtual image.

Question 7. 
State two differences between a convex and a concave lens.
Answer:
Differences between a convex and a concave lens

Question 8. 
Give one use each of a concave and a convex mirror.
Answer:
Concave mirror: This mirror is used by dentists to obtain a large virtual image of the teeth.
Convex mirror: The mirror is used in vehicle as rear view mirror, since they form the image of the objects spread over a large area.

Question 9. 
Which type of mirror can form a real image?
Answer:
Concave mirror can form a real image.

Question 10. 
Which type of lens forms always a virtual image?
Answer:
Concave lens always form a virtual image.

Choose the correct option in questions 11-13:
Question 11. 
A virtual image larger than the object can be produced by a:
(i) concave lens 
(ii) concave mirror 
(iii) convex mirror 
(iv) plane mirror 
Answer:
(ii) Concave mirror 

Question 12. 
David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be:
(i) 3 m 
(ii) 5 m 
(iii) 6 m 
(iv) 8 m
Answer:
(iii) If David moves 1 m towards the mirror then distance between his image and mirror = 4 - 1= 3 m.
So, distance between David and mirror
= 3 m.
Hence, distance between David and his image = 3 + 3 = 6 m.

Question 13. 
The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be :
(i) 1 m/s 
(ii) 2 m/s 
(iii) 4 m/s 
(iv) 8 m/s 
Answer:
(iii) 4 m/s.