NCERT Class VII Science Solutions: Chapter 15 – Light Part 2

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Question 4:

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

Answer:

Characteristics of the image formed by a plane mirror:

  • Virtual and erect.

  • Behind the mirror.

  • Size of image is equal to size of object.

  • Laterally inverted image (image of left side visible on right side).

  • Distance of image behind the mirror is equal to distance of object in front of mirror.

As showing in Image is a result for plane mirror

Result for Plane Mirror

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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:

A, H, I, M, O, T, U, V, W and X are the letters which form same image as the letter is. These letters are laterally symmetrical.

This image shows letters are laterally symmetrical

Letters Shows That Are Symmetrical

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Question 6:

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

Answer:

The image, which cannot be obtained on a screen, is called virtual image. The images formed by plane mirror, convex mirror and concave lens are virtual.

This diagram shows plane mirror, convex mirror and concave l …

Plane Mirror, Convex Mirror and Concave Lens Are Virtual

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Question 7:

State two differences between a convex and a concave lens.

Answer:

  • A convex lens can make images which are enlarged or smaller or equal to the size of the object whereas concave lens can always make smaller image.

  • A convex lens makes both real image and virtual images whereas a concave lens always makes a virtual image.

This diagram shows differences between a convex and a concav …

Differences between a Convex and a Concave Lens

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Question 8:

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

Answer:

  • Concave mirror is used by dentist, solar furnace, reflector of a torch, etc.

  • Convex mirror is used in rear view mirrors.