Question

• Take two tuning forks of the same frequency.
• Put some wax on the prongs of one of the forks.
• Vibrate both the tuning forks and keep them side by side.
• Listen to the periodic vibrations of loudness of resulting sound.
• How many beats have you heard in one minute?
• Can you guess whether frequency of tuning fork is increased or decreased by applying wax on the prong?
• How you can find the new frequency of the fork after applying wax on it.

Answer 1

• When wax is applied to one tuning fork, its effective mass increases. Therefore, its frequency decreases.
• The two forks now have slightly different frequencies and produce beats.

If N beats are heard in one minute, then the beat frequency is,

n = `N/60` Hz

If the original frequency of each tuning fork is ff, then the frequency of the waxed tuning fork is,

f' = `f - N/60`

Thus, by counting the number of beats produced in one minute, the new frequency of the tuning fork can be determined.