Question

If a person with long sightedness is given spectacles with concave lenses, will he/she have a
clear vision? Justify.​

Answer 1

Answer:

Concave prescription lenses (called as minus lenses) are used to bend light rays slightly outwards. The light rays then have a greater angle to bend back to focus when traveling through the cornea and lens. As a result, the light rays focus further back on the retina. So, the correct answer is option C.

Answer 2

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No, if a person with long sightedness (hypermetropia) is given spectacles with concave lenses, she/he won't have a clear vision. This is because in long sightedness, the person become unable to see clearly nearby objects. In that case, if the eye lens become more convergent ; then he/she will be able to see nearby objects clearly. To make the eye lens more convergent, convex lens is used.

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✰ Convex lens is used to converge the diverging rays of light coming from the object nearby in the front of hypermetropic eye. It increases the converging power of the eye lens. Thus, correcting the deflection of vision due to hypermetropia.

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✰ Why if person with long sightedness is given spectacles with concave lenses?

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$\dashrightarrow$ Concave lens is used to diverge the rays of light coming from the far object in the front of myopic eye ( suffering from short-sightdness) . It is used to reduce the converging power of the eye lens. Concave lens won't correct the vision of hypermetropic eye , but make it more uncomfortable to see the nearby objects. So, if a person with long sightedness is given spectacles with concave lenses, she/he won't have a clear vision.