Question

When a paper is kept at the focal point of concave mirror exposed to sunlight for some time, it catches fire because:

A) Burning point of paper is very small.
Reflected light rays have more energy.
C) Sun rays converge to the focal point resulting in a lot of energy concentrated at the point.
D) Sun rays diverge from the focal point resulting in a lot of heat energy diverging from the point.

Answer 1

Hint: There are two types of mirror concave and convex in which concave is converging type of mirror and the convex mirror is a type of diverging mirror. The concave mirror is a converging mirror and when the parallel rays fall on the concave mirror it gets converged at a point.

Complete step by step solution:
It is asked in the problem about the reason why when a paper is kept at the focal point of a concave mirror exposed to sunlight for some time, it catches fire and we need to find the correct answer for this problem.

A concave mirror is a converging mirror on which when a parallel rays fall then all the rays gets converted at a point which is known as the focus of the concave mirror and as all the rays coincide at one point and therefore the intensity at that point will increase and that is why when a paper is kept at the focal point of concave mirror exposed to a sunlight for some time the paper catches fire. The concave mirror forms a virtual and magnified image if the object is kept very close to the mirror and if the object distance is increased then the image size reduces and real image is formed.

The correct answer for this problem is option C.

Note: The convex and concave mirror have radius of curvature and also focal length which allows the parallel light to get concentrated or gets dispersed when it falls on the mirror .If sun light gets converged at a point then due to lights high intensity the screen can start burning.