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Class 7 science chapter 15 light NCERT solutions
Chapter 15: Light
N C E R T Textbook Questions Solved
1. Fill in the blanks:
a. An image that cannot be obtained on a screen is called—————.
b. The 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.
Answers:
a. virtual image
b. mirror
c. plane
d. real image
e. lens
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 forms 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 forms a real image. (T/F)
Answer:
a. False
b. True
c. True
d. False
e. False
3. Match the items given in Column I with one or more items of Column II.
Answer:
4. State the characteristics of the image formed by a plane mirror
Answer
Characteristics of the image formed by a plane mirror are as follows:
• The distance of the image from the mirror is the same as to that of the object.
• Size of the image is equal to that of the object.
• The image formed is erect and virtual
• Images formed is laterally inverted.
5. Find out the letters of the 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 A, H, I, M, O, T, U, V, W, X, Y alphabets form images in a plane mirror exactly like the letter itself because these alphabets are laterally symmetric.
6. What is a virtual image? Give one situation where a virtual image is formed.
Answer The image that cannot be obtained on a screen is called a virtual image. The image formed by a plane mirror is virtual.
7. State two differences between a convex and a concave lens.
Answer
8. Give one use each of a concave and a convex mirror.
Answer The mirrors used in the headlight of cars and scooters are concave mirrors. The side-view mirrors of vehicles are Convex mirrors.
9. Which type of mirror can form a real image?
Answer The concave mirror can form a real image.
10. Which type of lens forms always a virtual image?
Answer
A convex mirror form a virtual image.
Choose the correct option in questions 11–13
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 The answer is ii. concave mirror
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
The answer is (iii) 6 m
13. The rearview 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 rearview 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
The answer is (iii) 4 m/s