Question

A student uses spectacles of number + 2 for seeing objects.Commonly used lenses for his/her spectacles are.......
A) bi concave B) double concave
C) concavo convex
D) convexo concave

Answer 1

Answer:

Convexo convave

Explanation:

Convex lenses are known as negative lenses because they cancel the positive power.

The stude suffers from hypermetropia.

TRICK:

+ve power - Hypermetropia 《LONG SIGHT :: CONVEX LENS》

-ve power - Myopia 《SHORT SIGHT :: CONCAVE LENS》

It can not only be convexo concave, but any convex lens.

Answer 2

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C) Concavo convex

$\large\boxed{\fcolorbox{blue}{yellow} {Explanation }}$

1. A person suffering from hypermetropja can see distant objects clearly as the image of a distant object is formed on the retina, but cannot see nearby objects clearly as the image of a nearby object would be formed behind the retina instead of on the retina.

2. A convex lens converges the rays of light passing through it.

3. When spectacles of convex lenses of appropriate power are used, the rays of light coming from a nearby object are converged to proper extent before they are incident on the eye lens.

Therefore, after the converging action of the eye lens, the image of a nearby object is formed on the retina of the eye and hence the nearby object can be seen clearly.

Hope it helps!

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