Beat Frequency of 2 Waves in Free Space

In summary, the task is to find the beat frequency of two waves with different wavelengths (1.5μm and 1.63μm) that are combined in free space. The formula for beat frequency is (ω1- ω2) = 2ωm, where ωm is the beat frequency. To determine the frequencies of the constituent waves, the formula v = fλ can be used, assuming the velocity of the wave is c.
  • #1
nmsurobert
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Homework Statement


Two waves of different wavelengths λ1= 1.5μm, λ2 = 1.63μm, are combined in free space Et = 1.5cos(k1x - ω1t) + 2cos(k2x -ω2t)
Find the beat frequency

Homework Equations


1- ω2) = 2ωm=beat frequency

E02 = 4E012cos2(kmx - ωmt)

The Attempt at a Solution


I am quite stuck on this problem. Can I get a numerical solution for question with what I've been given?
 
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  • #2
nmsurobert said:
I am quite stuck on this problem. Can I get a numerical solution for question with what I've been given?

first you must superpose the two waves and see the waxing and waning of sound intensities and count its frequency per second.
that can be simply done on a plot of amplitude with time graph.
your amplitudes are different -so the destructive interference will not necessarily produce a zero intensity but the envelope of intensity and its maximum and minimum values will give you beat frequency.
so proceed ahead.
 
  • #3
nmsurobert said:

Homework Statement


Two waves of different wavelengths λ1= 1.5μm, λ2 = 1.63μm, are combined in free space Et = 1.5cos(k1x - ω1t) + 2cos(k2x -ω2t)
Find the beat frequency

Homework Equations


1- ω2) = 2ωm=beat frequency
Yes, you need to determine the beat frequency which is half the difference of frequencies of the constituent waves. You are given the wavelengths. What are the frequencies?
What kind of waves they are?
 
  • #4
ehild said:
Yes, you need to determine the beat frequency which is half the difference of frequencies of the constituent waves. You are given the wavelengths. What are the frequencies?
What kind of waves they are?
I don't know what kind of waves they are. I wrote the question as it is on the paper. I've been trying to figure out a way to find the frequency but I feel like I'm missing something.
 
  • #5
drvrm said:
first you must superpose the two waves and see the waxing and waning of sound intensities and count its frequency per second.
that can be simply done on a plot of amplitude with time graph.
your amplitudes are different -so the destructive interference will not necessarily produce a zero intensity but the envelope of intensity and its maximum and minimum values will give you beat frequency.
so proceed ahead.
Asking me to plot something isn't going to help haha he's been asking us to plot stuff all semester and I haven't been able to figure out how to plot any of this stuff.
 
  • #6
nmsurobert said:
I don't know what kind of waves they are. I wrote the question as it is on the paper. I've been trying to figure out a way to find the frequency but I feel like I'm missing something.
How do you get the frequency from the wavelength of the wave?
 
  • #7
ehild said:
How do you get the frequency from the wavelength of the wave?
The only way I've found how to do this is v = fλ. However, I don't know what the velocity of the way is unless I assume the velocity is c.
 
  • #8
nmsurobert said:
The only way I've found how to do this is v = fλ. However, I don't know what the velocity of the way is unless I assume the velocity is c.
Yes, the speed of the wave is crucial. it is said, the wave travels in free space. What do you think free space means? Was the original text English?
 
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  • #9
It was in English. I'll just assume that then. Sometimes the assignments are either vague or misleading for the class so I try not too assume too much. Thank you though! That makes the problem much easier lol
 

1. What is the beat frequency of two waves in free space?

The beat frequency of two waves in free space is the frequency at which the amplitude of the resulting wave (formed by the superposition of the two waves) varies. It is equal to the absolute value of the difference between the frequencies of the two individual waves.

2. How is the beat frequency of two waves in free space calculated?

The beat frequency can be calculated using the equation fb = |f1 - f2|, where f1 and f2 are the frequencies of the two individual waves.

3. What is the relationship between the beat frequency and the frequencies of the individual waves?

The beat frequency is directly proportional to the difference between the frequencies of the individual waves. This means that as the difference between the frequencies increases, the beat frequency also increases.

4. Can the beat frequency of two waves in free space be negative?

No, the beat frequency can never be negative. It is always a positive value as it represents the absolute value of the difference between the frequencies of the two waves.

5. How does the beat frequency change if the frequencies of the individual waves are the same?

If the frequencies of the two individual waves are the same, the beat frequency will be equal to 0. This is because there is no difference between the frequencies, resulting in no variation in the amplitude of the resulting wave.

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