Question

plz answer this question with explanation

Answer 1

Answer:

Given,

distance of flame from lens (u) = -60cm     [u is always -ve]

distance of screen from lens (v) = 20cm

By using mirror formula,

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

$\frac{1}{f}=\frac{1}{20} - \frac{1}{-60}$

$\frac{1}{f} = \frac{1}{20} + \frac{1}{60}$

$\frac{1}{f} = \frac{3+1}{60}$

$\frac{1}{f} = \frac{4}{60}$

$\frac{1}{f} = \frac{1}{15}$

Therefore,

f = 15

(b) The last observation i.e.,

v=12 and u=-70 is wrong because it doesn't satisfy the mirror formula

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Hope This Helps!

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Answer 2

Answer:

thanks for free points ok

thanks for free points ok

thanks for free points ok