Question

explain myopia..............

Answer 1

nearsightedness, also known as short sightedness and myopia, is a condition of the eyewear life focuses in front of comma instead of on the retina.



standard objects to be blood while close objects appear normal.

Answer 2

Answer:

Myopia (Short-sightedness):- Myopia is a defect in which a human eye can see nearby objects distinctly but is unable to see distant objects distinctly.

Explanation:

See the attachment .

The Far point shown . This point is generally a few metres from the eye .

It is because of this reason that students suffering from myopia are unable to read writing on black board from back benches.

The reason for Myopia are :

• High Converging power of eye-lens because ciliary Muscles Do not relax sufficiently.
• Eye ball being too long because of which the distance between eye-lens and retina increases.

Correction :- This defect is Corrected by placing a concave lens before the eye. The parallel rays coming from distant object is first diverged by the concave lens and then converged by the eye-lens.

The Power of concave lens is chosen such that it creates only that much divergence so that after the Converging action of eye-lens the image is formed on the retina

The Concave Lens forms image of an object placed at infinity $u = - \infty$is at F.

Here v = -(distance of far point from the eye) = -x.

Applying Lens formula For concave lens (the corrective lens) we get,

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$

$⟹ \frac{1}{ - x} - \frac{1}{ - \infty } = \frac{1}{f}$

$⟹P= \frac{1}{f} = \frac{1}{ - x}$

AS EXTRA INFORMATION !!

• Power of spectacles for a myopic eye is Negative because the focal length of concave lens is negative.
• Power of Concave lens is different from different myopic eye depending on the degree of defect.

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