Question

The power of a converging lens is 4.5 D and that of a diverging lens is 3 D. The power of this combination of lenses placed close together is (a) +1.5D
(b) +7.5D
(c) −7.5D
(d) −1.5D

Answer 1

Three steps solutions

Explanation:

Given data,

power of a converging lens = 4.5 D

And power of a diverging lens = 3 D

We know that ,

power of the combination of lenses = power of converging lens - power of diverging lenses

power of the combination of lenses  = 4.5 - 3

= 1.5

Answer 2

Option (a) is Answer

Explanation:

We know that,  

Power (P) of lens, adds up when they are placed in combination.

Therefore,  

• Net Power = $P_1 + P_2$

Here, Power of Converging Lens is $P_1$ = 4.5 D

• Power of Diverging Lens is $P_2$ = - 3.0 D

Hence,

Net power = $P_1 + P_2$

Net Power = 4.5 D + (- 3.0 D)

Net Power = 1.5 D

So, The power of the combination of lenses placed together is Option (a) = 1.5 D