Question

Let’s say we can hear a beat frequency of 2Hz from two tuning forks. The first tuning fork has a frequency of 100Hz. If wax is applied on the 2nd tuning fork, the beat frequency becomes 4Hz, what is the frequency of the 2nd tuning fork?

(a) 100Hz

(b) 98Hz

(c) 106Hz

(d) 104Hz

I have been asked this question in an online interview.

My doubt is from Waves in portion Waves of Physics – Class 11

Answer 1

Right choice is (b) 98Hz

Easiest explanation: As the initial beat frequency is 2Hz, the 2nd tuning fork can have a frequency of 98Hz or 102Hz. When wax is applied to the second tuning fork its frequency should decrease. On doing so the beat frequency has also increased, so the initial value of the frequency of the 2nd tuning fork must be lower than that of the first tuning fork.