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Question: Figure given below shows a beam of light converging at point P. When a concave lens of focal length ...

Figure given below shows a beam of light converging at point P. When a concave lens of focal length 16 cm is introduced in the path of the beam at a place O shown by dotted line such that OP becomes the axis of the lens, the beam converges at a distance x from the lens. The value x will be equal to –

A

12 cm

B

24 cm

C

36 cm

D

48 cm

Answer

48 cm

Explanation

Solution

f = – 16 cm u = +12cm v = + x

1f=1v−1u\frac { 1 } { \mathrm { f } } = \frac { 1 } { \mathrm { v } } - \frac { 1 } { \mathrm { u } } Ž 1−16=1x−112\frac { 1 } { - 16 } = \frac { 1 } { x } - \frac { 1 } { 12 }

= 4−348\frac { 4 - 3 } { 48 } = 148\frac { 1 } { 48 }

Ž x=48 cm\mathrm { x } = 48 \mathrm {~cm}