Question

Explain the power (with sign )of concave lens of focal 20 CM.

Answer 1

first we have to convert force in cm to m
20cm = 0.2m
p= 1/f
p= 1/0.2
p= 10/2
p= 5 diap.
as it is concave lens then power will be -5 diapter

Answer 2

Here is the answer dear!
we have a formula right?

1            
----   =   P(power)   ( When focal length is given in metres)
f


100          
----   =   P(power)   ( When focal length is given in centimetres)
  f   

substitute ur f value in the above formula

u get 5 Dioptre

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