Question

an object 15cm from concave lens having its focal length 20 cm find the distance​

Answer 1

Answer:

u = 15 cm , f = 20cm ,  v = ?

By using lens formula;

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

So,

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

$\frac{1}{v} = \frac{1}{20} - \frac{1}{15}$

$\frac{1}{v} = \frac{3-4}{60}$

v = - 60 cm

'-' indicates that the image will be real.

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