Chapter 13, Problem 3TE

Solution

To determine: A person can get sunburn on a cloudy day but not on the sunny day if he is behind a glass.

Answer:

The person behind the glass can’t get sunburn on even a sunny day because ultraviolet rays cannot cross the glass, and get sunburn on a cloudy day because clouds are opaque to visible light they alloy ultraviolet rays to pass through them.

Explanation:

The reason for the sunburn is the ultraviolet rays which reach to the Earth. As clouds are opaque to visible light, so on a cloudy day without reaching the sunlight the ultraviolet rays still reach to the Earth which cause sunburn.

The electrons of the glass are set into the vibration when ultraviolet rays incident on a glass, with the same frequency as the as that of the frequency of the waves. When the natural frequency of the glass and the incident ray is same, then the electrons in the glass becomes resonant. This cause an increase in amplitude of the electrons due to which they collide with their neighboring electrons and lose energy. After losing energy, electrons cannot re-emit ultraviolet rays, and the person behind the glass does not get sunburn even on a sunny day because the ultraviolet rays cannot cross the glass.

Conclusion:

Therefore, the person behind the glass can’t get sunburn even on a sunny day because ultraviolet rays cannot cross the glass, and get sunburn on a cloudy day because clouds are opaque to visible light they alloy ultraviolet rays to pass through them.