Question

An object is place in front of a spherical mirror of focal length -20cm at a distance of 30 cm. At what distance from the mirror a screen be placed in order to obtain a sharp image of the object in it?

Answer 1

From the question , we can say that the mirror used is a concave mirror.

f = - 20 cm

u = - 30 cm

v = ?

Mirror formula

1/f = 1/v + 1/u

1/-20 = 1/v  +  1/-30

1/v = 1/-20 - 1/-30

    = -1/20 + 1/30

LCM of 20 and 30 = 60

therefore, 1/v = (-3 + 2)/60 =  -1/60

1/v = -1/60

v = -60 cm

Therefore, the screen should be placed  60 cm in front of the concave mirror.

Answer 2

$\textbf{Answer is in Attachment !}$