Question

A concave mirror has a radius of curvature $2m$. The light coming from a distant source is incident on the mirror. What is the distance of the image of the source from the mirror?

& A.0.5m \\\ & B.1m \\\ & C.1.5m \\\ & D.2m \\\ \end{aligned}$$

Answer 1

Concave mirrors are able to produce both real and virtual images. The images will be upright if it is virtual or inverted if it is real. They can be behind the mirror if it is virtual or in front of the mirror if it is real. The image will be formed by the rays which are from a large distance so that we can assume it to be from infinity.

Complete step by step answer:
First of all let us discuss concave mirrors. When the inner surface of the spherical mirror is made reflecting, then it is known as a concave mirror. If the outer surface of the spherical mirror is made reflecting, then it is called a convex mirror. Images formed by a concave mirror will be inverted and real and also virtual and erect images.
In this question, it is mentioned that the light rays are coming from a large distance for a mirror of curvature $2m$.
Therefore we can take it as the object is at infinity. If the object is at infinity, then the image is formed at the focus.
As we know, radius of curvature is given by the equation,
$f=\dfrac{R}{2}$
Substituting the value of $R$ in it,
$f=\dfrac{2}{2}=1m$
Therefore image will be at
$f=1m$

So, the correct answer is “Option B”.

Note: Concave mirrors are usually seen in torches, searchlights and headlights of vehicles to get a strong parallel beam of light. They are also used as shaving mirrors to see a magnified image of our face. Dentists in general use concave mirrors to view magnified images of the teeth of their patients.