the far point of a miopic person is 80cm in front of eye. what is the nature and power of the lens required to correct the problem​

Part A

The nature of the lens required is a concave lens

Part B

The power of the lens required is -1.25 D

Explanation:

Part A

Myopia is the eye condition whereby the focus of light entering the eye is in front of the retina such that the vision of a myopic person is blurred

The given far point of the myopic person in question = 80 cm

To correct the problem, the focus of light entering the eye will be moved further to reach the retina, by means of a concave lens which makes distant objects appear to come from (form an image at) 80 cm

Part B

The lens formula is given as follows;

Where;

f = The focus of the lens (virtual focus)

= The distance of the object = ∞ (infinity)

= The distance of the image = -80 cm (virtual image formed in front of the mirror)

Plugging in the values, gives;

f = -80 cm = -0.8 m

The power of a lens, 'P' is the reciprocal of the focal length, 'f', given in meters

The SI unit for the power of a lens is the dioptre (D)

Therefore;

Therefore, the power of the lens required, P = -1.25 D.

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