Question

A concave mirror of focal length 20cm is placed 50 cm from the wall . how far from the wall an object will be placed to form it real image on the wall

Answer 1

here you go ☆☆

given:-

f = -20 CM
u = -50 CM

to find = v


we know by using mirror formula

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

$\frac{1}{v} - \frac{1}{50} = - \frac{1}{20}$

$\frac{1}{v} = - \frac{1}{20} + \frac{1}{50}$

$\frac{1}{v} = \frac{ - 5 + 2}{100}$

$\frac{1}{v} = \frac{ - 3}{100}$

$v = - \frac{100}{3}$

$v = 33.3 \: cm$


$<marquee> hope it helps..........✌✌$

Answer 2

Given that,

Focal length = -20 cm

Image distance = -50 cm

We need to calculate the object distance

Using formula of mirror

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

Where, v = image distance

u = object distance

f = focal length

Put the value into the formula

$\dfrac{1}{-20}=\dfrac{1}{-50}+\dfrac{1}{u}$

$\dfrac{1}{u}=\dfrac{1}{-20}+\dfrac{1}{50}$

$\dfrac{1}{u}=-\dfrac{3}{100}\ cm$

$u=-\dfrac{100}{3}\ cm$

$u=-33.33\ cm$

Hence, The object distance is 33.33 cm

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Topic : optics

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