CLASS TASK ON LENSES

As an object is moved close to the focus of a converging lens from infinity its image I. moves closer to the lens II. moves away from the lens. III. Remains the same size. IV becomes smaller. Which of the statements above is/are correct?

• II only

• 1 and III only

• IV Only

• III only

Concave lens is also called

• diverging lens

• converging lens

• convex lens

• none of the above

Power of a lens is defined as the reciprocal of its

• vertex

• optical center

• principal axis

• focal length in meters

A point on the principal axis at the center of lens is known as

• principal axis

• optical center

• principal focus

• focal length

As the focal length of a concave lens is positive, therefore its power should be

• negative

• positive

• always zero

If an ophthalmologist places a 3.00 diopter lens next to 0.75 diopter lens, the power of lens should be

The lens which is thin at center and thick at edges is

• concave lens

• convex lens

• biconcave

• biconvex

The lens which diverges light from a single point is

• concave lens

• convex lens

• biconvex lens

• all of the above

The distance between the optical center and principal focus is

• focal point

• radius

• 2focal length