Question

Find the distance and nature of image formed by the concave mirror when the rays are incident as shown in the figure.

• A. $\frac{80}{3}\text{cm}$, real image
• B. $\frac{40}{3}\text{cm}$, virtual image
• C. $\frac{40}{3}\text{cm}$, Real image
• D. $\frac{20}{3}\text{cm}$, virtual image

Answer 1

The correct option is C $\frac{40}{3}\text{cm}$, Real image


From the ray diagram we can conclude that,
the object is virtual point object. So, the image formed should be real.

Since object distance is measured along the direction of light and focal length in the opposite direction, we can write that,

$u=40\text{cm};f=-20\text{cm}$

Using mirror formula,
$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

We get,

$v=\frac{uf}{u-f}=\frac{\left(40\right)(-20)}{(40+20)}\Rightarrow v=\frac{-40}{3}\text{cm}$

Since, rays are converging at point, a real image is formed somewhere between focus and the pole of concave mirror.

Hence, option (c) is the correct answer.