Question

An eye specialist prescribes a number + 4.5 D to person for his glasses. The nature of lens and its focal length is:

Options

• Convex, 22.22 cm

• Concave, 22.22 cm

• Convex, 21.22 cm

• Concave, 21.22 cm

Answer 1

Convex, 22.22 cm

Explanation:

Positive power means the lens is convex.

$$f = \frac{100}{4.5}$$

= 22.22 cm