Question

Rays from the Sun converge at a point $15cm$ in front of a concave mirror. Where should an object be placed so that the size of its image is equal to the size of the object?

Answer 1

Step 1: Given information.

Distance from the sun is covered by rays $15cm$

Step 2. Concept to be used

The relation between focal length (f) and radius of curvature (R) of a spherical mirror is that the focal length is equal to half of the radius of curvature.

So,

$f={\displaystyle \frac{R}{2}}$.

Step 3: Find the distance where the object is placed.

In the case of a concave mirror.

So, we have $f=15cm$

As we know, the size of the image and object is the same if we placed the object at

$R=2f$.

$$\begin{gathered} =2\times 15 \\ =30cm \end{gathered}$$

Hence, the distance where the object is placed $30cm$.