Study Materials

# NCERT Solutions for Class 7th Science

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## Chapter 15. Light

Ques: Why is this suggested that we should not look directly toward the sun or its image?
Ans: Never look directly towards the sun or its image as it may damage your eyes. You may look at the image of the sun when it is thrown on a screen or a wall.

Ques: Why are convex mirror used mainly in vehicles as side mirror?
Ans: Convex mirrors can form images of objects spread over a large area. So, these help the drivers to see the traffic behind them.

Ques: Write three uses of concave mirrors?
Ans: Uses of concave mirrors.

(i) it is used by ENT doctors to see the ears, nose and throat and reflect the light.

(ii) The dentist uses it to get enlarge image of teeth.

(iii) The reflectors of torches, headlights of cars and scooters are concave in shape.

Ques: Write the differences between convex and concave lens.
Ans: The differences between convex and concave lens.

convex lens:

(i) It feels thicker in the middle than at the edges.

(ii) A convex lens converges (bends inward) the light.

(iii) It forms real and inverted images.

concave lens:

(i) It feels thinner in the middle than at the edges.

(ii) A concave lens diverges (bends outward) the light.

(iii) It forms virtual and erect images.

Ques: Why is word “AMBULANCE” written strangely on Ambulance?
Ans: When the driver of a vehicle ahead of an ambulance looks in
her/his rear view mirror, s/he can read ‘AMBULANCE’ written on it and give way to it.

Ques: What is Newton’s Disk?
Ans: When seven colours of rainbow pasting on the disk in their order rotates in daylight it seems white. Such disk is generally known as Newton’s disk.

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