Question

A divergent lens has a focal length of 30 cm. At what distance should an object of height 5 cm

from the optical centre of the lens be placed so that its image is formed 15 cm away from the lens?

Find the size of the image also.

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Answer 1

Here, f = −30 cmh1 = 5 cmv = −15 cmu = ?From the lens eqn. 1f=1v−1u⇒u=vff−v⇒u=−15×(−30)−30−(−15)=−30Thus the object has to be placed at a distance 30 cm from the lens.The magnification m=vu=−15−30=0.5⇒h2h1=0.5⇒h2=0.5h1=0.5×5=2.5 cmHere, f = −30 cmh1 = 5 cmv = −15 cmu = ?From the lens eqn. 1f=1v−1u⇒u=vff−v⇒u=−15×(−30)−30−(−15)=−30Thus the object has to be placed at a distance 30 cm from the lens.The magnification m=vu=−15−30=0.5⇒h2h1=0.5⇒h2=0.5h1=0.5×5=2.5 cm  

Thus height of the image formed is 2.5 cm

Answer 2

Please mark my answer as the brainliest

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