Question

a spherical mirror forms a three time magnified sharp image on screen when a object is placed at a distance of 20 cm from the mirror . Find the position of the screen andthe focal length of mirror​

Answer 1

Answer:

There is no need of any of these to work with

Answer 2

Ok guys here is your answer

the formula of magnificatio(m) = -v/u

so, as m= 3 then -v = 3u ----------( 1 )

now, as we know , the lens formula

1/f = 1/u + 1/v

so, 1/f = 1/u + 1/-3u ( from eq. 1 )

and we also know that " u = 20 cm"

so 1/f = 1/20 + 1/ -3(20)

by calculation we get ,

1/f = 2/60 after inversion of equation we get ,

f= 60/2 = 30 cm

So answer is 30 cm

I HOPE IT WILL HELP YOU ALL