Question

What is power of lens ?
Power of lens is mentioned as -2.5D , what it means, find it's focal length.

Answer 1

The power of lens is the focusing power
-2.5D means that the person is suffering from mypoia and is using a concave lens p=1/f(m) or 100/f(cm) -2.5=100/f
100/-2.5=f
40=f

Answer 2

POWER OF LENS:

*the ability of an eye to focus its focal length is called as power of lens

GIVEN:

P=-2.5D

p=1/f

-2.5=1/f

F=1/-2.5

F=-0.4m

F=-40cm.

the person is suffering from the defect-MYOPIA

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hope it helps