Question

A lens has a power of $+2D$. What is the nature and focal length of the lens?

Answer 1

Step 1: Given data

The power of the lens is $P=+2D$.

Step 2: Finding the nature of the lens.

As the power of the lens is positive, the lens used is convex.

Step 3: Finding the focal length of the lens.

According to the power of lens formula,

$P=\frac{1}{f}$

where $f$ is the focal length of the lens in meters.

Substituting the known values,

$$\begin{gathered} +2D=\frac{1}{f} \\ +2m^{-1}=\frac{1}{f} \\ 2=\frac{1}{f} \\ f=\frac{1}{2} \\ f=0.5m \\ f=50cm \end{gathered}$$

Thus, the focal length of the lens is $50cm$.