How to find the frequency of the second wave?

[nineteen]

Homework Statement

I have provided the question as a photograph. Please refer to that.

Relevant Equations

Beat frequency = Frequency of wave 2 - Frequency of wave 1

I don’t understand how to approach this. So I couldn’t make an attempt at a solution. Please help me understand better. Thank you in advance.

 

[Delta2]

As you write in the equations section , beat frequency=frequency of wave 2-frequency of wave 1.
The beat frequency is the frequency of the combined signal, that is signal (B). Frequency of wave 1 is the frequency of signal (A), while frequency of wave 2 is the frequency of the unknown signal (C).

What can you tell, by observing the waveforms A and B, about the frequency of signal (A) in relation to the frequency of signal (B)? How many times bigger or how many times smaller is the frequency of signal (A) than that of (B)?

 

[nineteen]

As you write in the equations section , beat frequency=frequency of wave 2-frequency of wave 1.
The beat frequency is the frequency of the combined signal, that is signal (B). Frequency of wave 1 is the frequency of signal (A), while frequency of wave 2 is the frequency of the unknown signal (C).

What can you tell, by observing the waveforms A and B, about the frequency of signal (A) in relation to the frequency of signal (B)? How many times bigger or how many times smaller is the frequency of signal (A) than that of (B)?

Hey, I know the answer also, the answer is 60Hz. I just want an explanation of how it came because.

 

[nineteen]

The correct answer is 3) 60Hz. I just want an explanation on how it became the answer.

 

[haruspex]

The correct answer is 3) 60Hz. I just want an explanation on how it became the answer.

It is not entirely clear whether you asking how the equation you quote is justified or how to apply it in this case. Maybe both?
For how to apply, look at B. The magnitudes of the rapid oscillations are at a minimum where the vertical dotted lines have been drawn. So from one such line to the next is one period of the beat. Given that A shows 50Hz, what is the beat frequency in B?

 

[Delta2]

It is against the rules of these forums to provide you with a full detailed solution, without you showing some effort to participate in the solution steps.
So please participate and try to answer my question (or Haruspex's question in post #5). What can you say about the frequency of the combined signal B just by observing the waveforms in the figure and especially by comparing the parts between the dotted lines?

 

[nineteen]

It is against the rules of these forums to provide you with a full detailed solution, without you showing some effort to participate in the solution steps.
So please participate and try to answer my question (or Haruspex's question in post #5). What can you say about the frequency of the combined signal B just by observing the waveforms in the figure and especially by comparing the parts between the dotted lines?

I found the way. 5 waves in a certain time duration gives 50Hz. For the same time duration it only shows 1 beat in wave form B. Given that, after combining the 50Hz frequency and the frequency f the beats per that certain time is 1. As the equation says the beat frequency is the difference between the two combined frequencies, and here the difference of the two frequencies gives 1 beat per unit time. 5 waves gives 50 Hz (5 x 10) and 1 beat should also give the multiplication of it by 10 as its frequency. So the real beat frequency is 10 Hz. The question mentions that the frequency f is greater than 50 Hz. So what frequency greater than 50 Hz here gives difference between it and 50 Hz as 10 Hz. None other than 60 Hz. So the answer is 60 Hz. Am I correct?

@haruspex you also please check whether my solution is right or wrong.

Thank you both @Delta2 and @haruspex

 

[Delta2]

Well, you are correct mostly. The only thing that seems abit vague to me is your explanation on why the beat frequency is 10Hz. Other than that all is good.