Question

Two lenses of power 3.5 diopter and 1.5 diopter are placed in contact

Answer 1

power =1/focal length

focal length =f1+f2 combined focal length =1/3.5+1/1.5=0.95 approx

power =1/0.95=0.1approx

Answer 2

The power of the combination is 5 D.

Explanation:

It is given that,

Power of lens 1, $P_1=3.5\ D$

Power of lens 2, $P_2=1.5\ D$

It is assumed to find the power of the combination when they are in contact with each other. It is given by the sum of powers of individual lenses. Let it is equal to P. So,

$P=P_1+P_2$

$P=3.5+1.5$

P = 5 D

So, the power of the combination is 5 D. Hence, this is the required solution.

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