Question

The focal of the combination of convex lens power 1D and concave lens of power -1.5 D is

Answer 1

Given ,

The power of lens of convex and concave lens are 1 D and - 1.5 D

We know that ,

The power of lenses in contact is given by

$\boxed{ \tt{P = P' + P" + ...}}$

Thus ,

P = 1 + (-1.5)

P = 1 - 1.5

P = -0.5 D

Now , The power of lens is inverse of focal length

$\boxed{ \tt{P = \frac{1}{F}} }$

Thus ,

F = -1/0.5

F = -2 m

Hence , the equivalent focal length of convex and concave lens is -2 m