Question

A converging lens of focal length 5cm is placed at a distance of 20cm from a screen how far from the lens should an object be placed so as to form its real image on the screen?

Answer 1

$\huge\mathfrak {Answer:-}$

Given:-

Focal length of the convex lens $(f)$ $=5\:cm$

Image distance $(u)$ $=20\:cm$

Now,

Using the lens formula,

We get,

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

$\frac{1}{u} = \frac{1}{20} - \frac{1}{5}$

$\frac{1}{u} = \frac{1 - 4}{20}$

$u = - \frac {20}{3} \: cm$

$u = - 6.33 \: cm$

Hence,

The object should be placed at $6.33\:cm$ from the lens.

$\huge {Be\:Brainly}$❤️

Answer 2

Focal length of the convex lens (f)  = 5 cm
Image distance (u) = 20 cm
Let the object distance from the lens be u.
Now, using the lens formula:
1/f = 1/v - 1/u
1/u = 1/20 - 1/5
u = -20/3 cm

u = - 6.33 cm

Hence, the object should be kept 6.33 cm in front of the lens.