Two tuning forks are sounded at the same time.

Which tuning forks will give a beat frequency of 20 Hz when sounded with a 240 Hz tuning fork? select all that apply.

12 Hz 220 Hz 4800 Hz 260 Hz

What is the beat frequency heard for each pair of tuning forks below?

1. 240 Hz and 270 Hz

2. 300 Hz and 325 Hz

3. 440 Hz and 460 Hz

A. 625 Hz

B. 20 Hz

C. 900 Hz

D. 30 Hz

E. 25 Hz

F. 510 Hz

First part: 220Hz and 260Hz

Second part:

1. D 2. E 3. B

Explanation:

Beat frequency refers to the difference of the frequencies of two instruments which are sounded together. They occur as a result of the interference of the frequencies of two waves.

Beat frequency = f2 - f1

Where f1 is the frequency of instrument with lower frequency

f2 is the frequency of instrument with higher frequency

First part: We are trying to achieve a beat frequency of 20Hz and we have a tuning with natural frequency 240Hz. We are given a list of tuning forks with frequency 12Hz, 220Hz, 4800Hz, 260Hz.

for 12Hz; beat frequency = 240-12 = 228Hz

220Hz; beat frequency = 240-220 = 20Hz

4800Hz, beat frequency = 4800-240=4560Hz

260Hz; beat frequency = 260-240 = 20Hz

It is seen that beat frequency of 20Hz can be achieved by only the tuning fork of frequency 220Hz and 260Hz.

Second Part:

1. Beat frequency = 270-240 = 30Hz (option D)

2. Beat frequency = 325-300 = 25Hz (option E)

3. Beat frequency = 460-440 = 20Hz (option B)