Question

A spherical mirror and a thin spherical lens have focal length of -10cm. The mirror and lens are likely to be-

a.Both convex


b.Both concave


c.The mirror is convex and lens is concave


d.The mirror is concave and lens is convex​

Answer 1

it is said to be a concave lens because the focal length of this lens is -10cm

Answer 2

The mirror and lens are likely to be- d.The mirror is concave and lens is convex​

• Negative focal length represents that the focus is on the same side as that of the object.
• In concave mirror, the focal point is in front of the mirror. Objects are also placed in front of the mirror. Thus, the concave mirror has a negative focal length.
• In the case of lens, diverging lens always has a negative focal length. Convex lens is a diverging lens. Hence, it will always have negative focal length.