NCERT Class 7 Science Chapter 15 - Light

Chapter 15 - Light

Question and Answers
Question 1: Fill in the blanks
a) An image that cannot be obtained on a screen is called virtual image.
b) Image formed by a convex mirror is always virtual and smaller in size.
c) An image formed by a plane 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 real image.
e) An image formed by a concave lens cannot be obtained on a screen.

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. (False)
b) A concave lens always forms a virtual image. (True)
c) We can obtain a real, enlarged and inverted image by a concave mirror. (True)
d) A real image cannot be obtained on a screen. (False)
e) A concave mirror always forms a real image. (False)

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

Question 4: State the characteristics of the image formed by a plane mirror.
Answer: The characteristics of the image formed by a plane mirror are:
1. Image distance and object distance are equal.
2. Size of the objects and images are equal.
3. The image formed is erect and virtual.

Question 5: Find out the letters of English alphabets or any other languages known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.
Answer: Alphabets like A, H, I, M, O, T, U, V, W, X and Y form images in a plane mirror exactly like the letter itself.

Question 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 virtual image. The image formed by a plane mirror is virtual. The image formed by a plane mirror is virtual.

Question 7: State two differences between a convex and a concave lens.
Answer: Convex lens
*It is thick in the middle and thin at the edge.
*Image formed is real.
Concave lens
*It is thin in the middle and thick at the edges.
*Image formed is virtual.

Question 8: Give one use each of a concave and a convex mirror.
Answer:
Concave mirror: It is used in headlights of various vehicles.
Convex mirror: It is used as side view mirrors in vehicles.

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

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

Question 11: A virtual image is larger than the object can be produced by a
a) Concave lens
b) Concave mirror
c) Convex mirror
d) Plane mirror
Answer: b) 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
a) 3 m
b) 5 m
c) 6 m
d) 8 m
Answer: c) 6 m

Question 13: The rear view mirror of a car is a plane mirror. A driver is reversing his car at the speed of 2m/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
a) 1 m/s
b) 2 m/s
c) 4 m/s
d) 8 m/s
Answer: c) 4 m/s