Question

d) A spherical mirror and a thin spherical lens have each a focal length of
-15cm. The mirror and the lens are likely to be
i) Both concave
1) both convex
in the mirror is concave and the lens is convex
ivl the mirror is convex, but the lens is concave.
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Answer 1

Given that,

Focal length of spherical mirror = -15 cm

Focal length of spherical lens = -15 cm

We know that,

Concave mirror or lens :

The mirror or thin lens which the focal length is negative. It is called concave mirror or concave lens.

Convex mirror or lens :

The mirror or thin lens which the focal length is positive. It is called convex mirror or convex lens.

We need to find the mirror and the lens are likely to be

Using formula of focal length

The focal length of the mirror and a thin spherical lens is negative.

So, The spherical mirror and thin spherical lens are concave.

Hence, Both concave.

(i) is correct option.