Question

In a convex mirror the focal length is 30cm. Image formed is twice the size of pencil . Find the distance of the object from the mirror​

Answer 1

Answer:

Given

f= - 30 cm

we have given that mirror is converging means concave mirror and image formed is twice the size of the object means image formed is behind the mirror and is larger in size. so, we take f in negative sign.

h'= 2h

u= ?

now,

m= - v/u = h'/ h

= -v / u = 2h / h

= -v / u = 2

= -v = 2u

= v = -2u

As we know that

1/f = 1/ v + 1/ u

1/-30 = 1 / -2u + 1/ u

-1/30 = -1/ 2u + -1+2/ 2u

-1/30 = +1/2u

2u= -30 cm

u = -15 cm.