Question

Paper burn when sun rays are allowed to fall on a point through concave mirror. Give reason

Answer 1

Convex Lens Concentrates The Light Energy To One Spot On The Paper So That The Heat  Energy Accumulates On That One Small Spot Of Paper.

As The Heat Increases, Combustion Will Occur When The Spot Becomes Too Hot & The Paper Burns.

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Answer 2

The parallel rays of the sunlight strike the concave mirror and meet at a point called principal focus.

The huge amount of light energy is concentrated on a single point .This leads to rise in temperature at that point.

When the ignition temperature of paper is crossed, it catches fire.

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