Question

ques1:What is cataract?What is done to restore the vision of a cataract affected eye?
ques2: Draw a diagram to show dispersion of white light by the prism why do we get different colours of light?
ques3: Define power of lens with its unit.One of two lens having power 4D and -2D are combined what is the total power and focal length of new lens


Please answer these questions as soon as possible and answercorrectly
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Answer 1

At old age the lens becomes milky and cloudy which results in partial or complete loss of vision . It can be corrected by using a cataract surgery.

Answer 2

Cataract happens when the eye lens become cloudy and milky.

Cataract can be cured using surgery

Since each colour coming out of the prism has different different wavelengths, hence the bend in different positions. Hence we see the 7 colours distinctly

The degree of convergence or divergence is expressed in terms of its power. Power is defined as the reciprocal of focal length.

Power unit is dioptre.

Total power = 4+(-2) = 2D

Focal length also equals to reciprocal of power

So focal length = 1/2 = 0.5m = 50cm