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

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Solution

(a) 1.5D
Because power of lens adds up when placed in combination.
Therefore
Net power = 4.5 D + ( $-$ 3.0 D) = 1.5 D

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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

(a) 1.5D Because power of lens adds up when placed in combination. Therefore Net power = 4.5 D + (-3.0 D) = 1.5 D

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

(a) 1.5D
Because power of lens adds up when placed in combination.
Therefore
Net power = 4.5 D + ( $-$ 3.0 D) = 1.5 D