# NCERT Solutions for Class 7 Science Chapter 15

## Light Class 7

### Exercise : Solutions of Questions on Page Number : 189

Q1 :

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.

(a) An image that cannot be obtained on a screen is called _virtual image_.

A virtual image cannot be obtained on a screen. Only real images can be obtained on a screen.

(b) Image formed by a convex __mirror__is always virtual and smaller in size.

A convex mirror forms a virtual, diminished and upright image of an object.

(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.

Only real images can be obtained on a screen.

(e) An image formed by a concave __lens__cannot be obtained on a screen.

The image formed by concave lens is always virtual. A virtual image cannot be obtained on a screen.

Q2 :

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)

(a)False

The image formed by a convex mirror is always virtual, diminished and erect.

(b) True

The image formed by a concave lens is always virtual, erect and diminished.

(c) True

The image formed by a concave mirror can be real or virtual, enlarged or diminished, and erect or inverted, depending upon the distance of the object from the mirror.

(d) False

The image that can be obtained on a screen is called a real image. Virtual images cannot be obtained on a screen.

(e) False

A concave mirror can form both real and virtual images. The nature of the image depends on the distance of the object from the mirror.

Q3 :

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 the object.

Q4 :

State the characteristics of the image formed by a plane mirror.

Q5 :

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.

Q6 :

What is a virtual image? Give one situation where a virtual image is formed.

Q7 :

State two differences between a convex and a concave lens.

Q8 :

Give one use each of a concave and a convex mirror.

Q9 :

Which type of mirror can form a real image?

Q10 :

Which type of lens forms always a virtual image?

Q11 :

A virtual image larger than the object can be produced by a

(i) concave lens

(ii) concave mirror

(iii) convex mirror

(iv) plane mirror

Q12 :

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

Q13 :

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 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