Question

Define the power of a lens. What is the meaning of “The power of a lens is 1 diaptor” If the power a of a lens is -2.0 D, then what type of lens is that? When an object is kept at infinity from this type of lens, what is the size of the image formed?.

Answer 1

the power of lens

S.I unit = dioptre
1 d = 1/f

d= - 2.0

d=1/f

-2.0=1/f

f = 1/-2.0
f = 5 cm

power is in minius in cancave lens

u = -infinity
f = -5 cm

1/v - 1/u = 1/f

1/v = 1/f + 1/u

1/v = 1/-5 + 0 - ( 1/infinity = 0)

1/v = 1/-5

v = -5 cm

real .
at c .
erect .

I hope this will help you...