Question

the focal length of spectacle without power is:
a.0
b.1
c.infinity
d.none of these​

Answer 1

the focal length of spectacle without power is 0

Answer 2

To find:

The focal length of spectacle without power?

Calculation:

• Power is the converging/diverging ability of a lens.

• No power means zero power. This means that the lens doesn't have any power to converge or diverge a light ray.

• Light ray incident on this spectacle will not get deviated.

Let focal length be f :

$\therefore \: f = \dfrac{1}{power}$

$\implies \: f = \dfrac{1}{0}$

$\implies \: f = \infty$

So, focal length of lens is infinity.