Question

A concave mirror of radius of curvature 30cm produces images of magnification 2. Find two possible values of u and v.

Answer 1

Focal length=f=30cm

M=3

i.e

q/p=3

Case 1: When q is positive

q=3p

positiOn of object=p=?

Using spherical mirror formula

1/f=1/p+1/q

1/30=1/p+1/3p

1/30=(3+1)/3p

1/30=4/3p

3p=120

p=40

pOsition of object is 40cm from mirror.

Case 2:

when q is negative then

q=-3p

positiOn of object=p=?

Using spherical mirror formula

1/f=1/p+1/q

1/30=1/p+1/-3p

1/30=(3-1)/3p

1/30=2/3p

3p=60

p=20

pOsition of object is 20cm from mirror.