Question

At what distance the object should be placed so that the image will be formed at a distance 10 cm
from a concave lens? Focal length of the lens is 20 cm.

Answer 1

Answer:plz refer attachment

Explanation:plz mark as brainlist

Answer 2

Answer:

The object distance is -20 cm

Explanation:

Given data :

Image distance (v) = -10 cm

Focal length ( f) = -20 cm

To be calculated : Object distance

Formula to he used :

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$

where f is focal length, u is object distance and v is image distance.

f is focal length, u is object distance and v is image distance.Calculations :

$\frac{1}{( - 20)} = \frac{1}{u} + \frac{1}{( - 10)} \\ \frac{1}{u} = \frac{ - 1}{10} - \frac{( - 1)}{20} \\ \frac{1}{u} = \frac{ - 2 + 1}{20} = \frac{( - 1)}{20} \\ u = - 20 \: cm$

Hence, the object distance is -20 cm

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