# NCERT Solution class 7 Science Chapter-15

Chapter – 15          Light

Chapter Exercise

Page no. – (189)

Q.1– Fill in the blanks:-

1. An image that cannot be obtained on a screen is called ____.
2. Image formed by a convex ____ is always virtual and smaller in size.
3. An image formed by a ____ mirror is always of the same size as that of the object.
4. an image which can be obtain on a screen is called a __real__ image.
5. An image formed by a concave __lens__ cannot be obtained on a screen.

Ans.1

1. An image that cannot be obtained on a screen is called __ virtual image __.
2. Image formed by a convex __ mirror __ is always virtual and smaller in size.
3. An image formed by a __ plane __ mirror is always of the same size as that of the object.
4. an image which can be obtain on a screen is called a __real__ image.
5. An image formed by a concave __lens__ cannot be obtained on a screen.

Q.2– Mark ‘T’ if the statement is true and ‘F’ if it is false:-

1. We can obtain an enlarged and erect image by a convex mirror. (T/ F)
2. A concave lens always from a virtual image. (T/ F)
3. We can obtain a real, enlarged form a virtual image. (T/ F)
4. A real image cannot be obtained on a screen. (T/ F)
5. A concave mirror always form a real image. (T/ F)

Ans.2

1. False.
2. True.
3. True.
4. False.
5. False.

Q.3– match the items given in column I with one or more items of Column II.

 Column I Column II a. A plane mirror i. Used as a magnifying glass b. A convex mirror ii. Can form image of objects spread over a large area c. A convex lens iii. Used by dentists to see enlarged image of teeth d. A concave mirror iv. The image is always inverted and magnified e. A concave lens v. The image is erect and of the same size as the object vi. The image is erect and smaller in size than object

Ans.3

 Column I Column II a. A plane mirror v. The image is erect and of the same size as the object b. A convex mirror ii. Can form image of objects spread over a large area c. A convex lens i. Used as a magnifying glass d. A concave mirror iii. Used by dentists to see enlarged image of teeth e. A concave lens iv. The image is always inverted and magnified

Q.4– State the characteristics of the image formed by a plane mirror.

Ans.4The following are the characteristics of the image formed by a plane mirror:-

• Plane mirror forms a virtual image.
• Plane mirror forms an erect image.
• The image are literally invert.
• The size of image is equal to size of object.
• The Distance of image behind the mirror is equal to distance of object in front of mirror.

Q.5Find 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.

Ans.5– A, H, I, M, O, T, U, V, W, X etc.

Q.6– What is a virtual Image? Give one situation where a virtual image is formed.

Ans.6The image that cannot be formed on a screen is known as virtual image. The image formed by Convex, plane mirror and concave lens are virtual image.

Q.7– State two different between a convex and a concave lens.

Ans.7

 S. No. Covex Lens Concave Lens 1. Thick in the middle and thin in edge Thinner in the middle and thick in edge 2. Formed a virtual Image Formed a real Image

Q.8– Give one use each of concave and a convex mirror.

Ans.8

• Concave Mirror:- Used by dentist to teeth in big size.
• Convex Mirror:- Used in real view mirrors.

Q.9– Which type of mirror can form a real image?

Ans.9The concave mirror can form a real image.

Q.10– Which type of lens forms always a virtual image?

Ans.10The convex lens forms always a virtual image.

Choose the correct option in questions 11 – 13

Q.11– A virtual image larger than the object can be produced by a

1. Concave lens
2. Concave mirror

iii. Convex mirror

1. Plane mirror

Ans.11ii. Concave mirror.

Q.12David 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

1. 3 m
2. 5 m

iii. 6 m

1. 8 m

Ans.12iii. 6 m

Q.13The 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 mew 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

1. 1 m/ s
2. 2 m/ s

iii. 4 m/ s

1. 8 m/ s

Ans.13– iii. 4 m/ s.