Chapter 13, Problem 4RQ

To determine

The fate of energy in ultraviolet light incident on glass.

Answer to Problem 4RQ

The ultraviolet gets absorbed by the glass.

Explanation of Solution

When ultraviolet waves shine on glass, resonance occurs. The vibration of electrons builds up to large amplitudes, just as pushing someone at the resonant frequency on a swing builds to large amplitude. The energy received by a glass atom is either re-emitted or passed on to the neighboring atoms by collisions.

The resonating atoms in the glass can hold onto the energy of ultraviolet light for quite a long time. During this time, the atom makes about one million vibrations. This time is enough to collide with neighboring atoms and release its energy as heat. The glass is, therefore, not transparent to ultraviolet. The ultraviolet gets absorbed by the glass.

Conclusion:

Therefore, the ultraviolet gets absorbed by the glass.