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
• B. reflected light rays have more energy
• C. sun rays converge to focal point resulting in lot of heat energy concentrated at the point
• D. sun rays diverge from focal point resulting in lot of heat energy diverging from the point

Answer 1

The correct option is C sun rays converge to focal point resulting in lot of heat energy concentrated at the point

When a concave mirror is exposed to the sun, all the incident sun rays are converged to the focal point and hence energy radiations are focussed at a single point. Hence, paper burns when it is kept at the focal point.