Question

A concave mirror of curvature 40 cm,
used for shaving purpose produces image
of double size as that of the object. Object
distance must be
(A) 10 cm only
(B) 20 cm only
(C) 30 cm only
(D) 10 cm or 30 cm​

Answer 1

Answer:

(D). 10 cm or 30 cm

Explanation:

We know that,

A concave mirror produces the image larger then the size of the object placed in front of it when the object is placed in between the Pole and Focus or when the object is placed in between the Focus and Radius of Curvature.

So,

Focus is at, F = 20 cm from the pole.

And,

Radius of Curvature, C = 40 cm

So,

For the image to be twice the size we can put it before 20 cm (< 20 cm.)

Or,

We can place it in between 20 cm and 40 cm (30 cm.)

Therefore, the possible distance is 10 cm or 30 cm.

Hence, the correct option is (D).