NCERT Class VII Science Solutions: Chapter 15 – Light Part 3

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Question 14:

Boojho made light from a laser torch to fall on a prism. Will he be able to observe a band of seven colours? Explain with a reason.

Answer:

No, laser torch gives out light of only one colour.

Question 15:

State the correct sequence (1-7) of colours in the spectrum formed by the prisms A and B. shown in Figure.

As showing in images is a spectrum formed by the prisms A an …

Spectrum Formed by the Prisms a and B. (Q)

Answer:

As showing in images is a spectrum formed by the prisms A an …

Spectrum Formed by the Prisms a and B. (A)

Question 16:

The side mirror of a scooter got broken. The mechanic replaced it with a plane mirror. Mention any inconvenience that the driver of the scooter will face while using it?

Answer:

The driver will not be able to see traffic spread over a large area behind him.

Question 17:

The concave reflecting surface of a torch got rusted. What effect would this have on the beam of light from the torch?

Answer:

The beam of light will be diffused with lower intensity.

Question 18:

An erect and enlarged image of an object is formed on a screen. Explain how this could be possible.

Answer:

The image formed on the screen could be enlarged and erect if the object is placed upside down between F and 2F of the lens.

Question 19:

Two different type of lenses are placed on a sheet of newspaper. How will you identify them without touching?

Answer:

If the letters appear bigger/magnified, then the lens is a convex lens. If the letters appear smaller, then the lens will be concave lens.

Image of difference between concave and convex lens

Difference between Concave and Convex Lens

Question 20:

A shopkeeper wanted to fix a mirror which will give a maximum view of his shop. What type of mirror should he use? Give reason.

Answer:

He will fix a convex mirror because it can form images of object spread over a large area.

Question 21:

The distance between an object and a convex lens is changing. It is noticed that the size of the image formed on a screen is decreasing. Is the object moving in a direction towards the lens or away from it?

Answer:

The object is moving away from the lens.

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