Question

Assertion (A): A converging mirror is pointed towards the sun. A piece of paper is then held in front of converging mirror in such a way that the sharpest point of reflected sunlight is obtained on the paper. Keep the paper in this position for a few minutes. The paper burns at the point of bright light and a hole is formed in it. 

Reason (R): The converging mirror concentrates a lot of sun’s rays to a small point on paper (called focus). The heat energy of these concentrated sun rays burns the paper to form a hole in it.

Options

• Both A and R are true and R is correct explanation of the assertion.

• Both A and R are true but R is not the correct explanation of the assertion.

• A is true but R is false.

• A is false but R is true.

Answer 1

Both A and R are true and R is correct explanation of the assertion.

Explanation:

Assertion (A) is true because a converging (concave) mirror focuses parallel sunlight into a highly concentrated, bright point. Reason (R) is true and perfectly explains the event, noting that this bright point is the principal focus where massive amounts of heat energy accumulate. Keeping the paper at this focal spot for a few minutes allows the extreme, localised heat buildup to cross the ignition point and burn a hole through it.