Question

The power of a convex lens of focal length 50 cm is ______.

Answer 1

Answer:

2 Dioptre ( 2 D)

Explanation:

Heya,

Power of a lens is related by its focal length as

$power \: = \frac{1}{f(in \: m \: )}$

OR

$power = \geqslant \frac{100}{f(in \: cm)}$

1. Focal length of a convex lens is positive
2. Focal length of a concave lens is negative.

Hence, power of the given convex lens is

$\frac{100}{50} = 2$

Regards

Kshitij

Answer 2

Topic - Convex Lens

• Power of a convex lens: The power of a convex lens is the reciprocal of its focal length.

• Unit: Its unit is dioptres $(D)$.
• $1\:D=1\:m^{-1}$

• Formula: If $P$ dioptres be the power of a convex lens and $f$ be its focal length, measured in metres, then
• $\quad\quad P=\frac{1}{f}$.

Solution:

Given, $f=50$ cm $=0.5$ m

Using the above formula, we get

$\quad P=\frac{1}{0.5}$

$\Rightarrow P=\frac{10}{5}$

$\Rightarrow P=2$

Answer: The power of a convex lens of focal length $50$ cm is $2\:D$.