A double convex lens has two surfaces of equal radii R and refractive index m = 1.5. We have,

1. f = R/2

2. f = R

3. f = - R

4. f = 2R

A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power of a cut-lens will be

1. 2 D

2. 3 D

3. 4 D

4. 5 D

A thin lens is made with a material having refractive index \(\mu\) = 1.5. Both the sides are convex. It is dipped in water (\(\mu\) = 1.33). It will behave like

1. a convergent lens

2. a divergent lens

3. a rectangular slab

4. a prism

A convex lens is made of a material having refractive index 1.2. Both the surfaces of the lens are convex. If it is dipped into water (\(\mu\) = 1.33), it will behave like

1. a convergent lens

2. a divergent lens

3. a rectangular slab

4. a prism