Question

How to calculate power of eye for class 10 physics?

Answer 1

Power can be calculated just by finding the reciprocal ( Multiplicative inverse) of Focal length of that lense...

Once you get the focal length and any of these lens whether it is Concave or Convex...just reciprocal it...you will the power of that lense..

if Power = P and f = Focal length then P = 1 / f

The unit of Power is Diopter denoted by symbol D

Convex lens is found in human eye...and the focal length of convex lense is always positive...So whatever Power you get is always positive too...

Example : -

The focal length of a convex lense is 50cm . calculate its power..

Focal length f = + 50cm = 50 x 1/100 m ( unit must be in Meters)
f = 0.2 m
We know that P = 1 / f

P = 1 / 0.2 = 10 / 2 = 5 Dioptre or +5D

Simillarly we can calculate the power of Concave lense which have negative focal length...so You can use the same formula to get the power of Concave lense...Remember one thing that...

Focal lenght of a convex lense is always positive so its power will be positive too and for the concave lense focal length is negative so its power will be negative too...

This is how you can calculate the power of any lense...Hope this help...