Why don't we use arc length formula to calculate wavelength?

In summary, the conversation discusses the use of arc length formula to calculate wavelength and the suggestion to treat the length of a sine function between two points instead. However, it is noted that this measurement would not be useful and that the traditional definitions of wavelength and amplitude are important. The misunderstanding of wavelength due to the way EM waves are often drawn in books is also mentioned.
  • #1
LLT71
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5
can you please explain me why don't we use arc length formula to calculate wavelength? seems a bit confusing...
 
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  • #2
Could you please be more specific?
 
  • #3
Wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests, or troughs, or corresponding zero crossings as shown.
Why don't we treat that as length of sine function between that two points instead, cause that would give us full length of that function in that interval? This way it seems to me like "length of a line" between two points (crests etc.)=wavelength.
 
  • #4
Well for one, that measurement wouldn't be useful. Wavelength as it is currently defined has a lot of physical meaning. Some sort of length along the curve does not.
 
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  • #5
LLT71 said:
Why don't we treat that as length of sine function between that two points instead, cause that would give us full length of that function in that interval?
If you have a sin function usually the vertical axis is something like E field strength or pressure, not distance. So it usually wouldn't make sense unit-wise to use the arc length formula.
 
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  • #6
LLT71 said:
Wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests, or troughs, or corresponding zero crossings as shown.
Why don't we treat that as length of sine function between that two points instead, cause that would give us full length of that function in that interval? This way it seems to me like "length of a line" between two points (crests etc.)=wavelength.

It's an interesting idea. That would actually be a combination of the wavelength and the amplitude. If you think about music, and notes on a stringed instrument, you can see why the traditional definitions of wavelength and amplitude are important.
 
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  • #7
thank you all! I think seeing a wave just in a way of math function and not understanding what that function actually represents led me to misinterpret wavelength.
 
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  • #8
LLT71 said:
thank you all! I think seeing a wave just in a way of math function and not understanding what that function actually represents led me to misinterpret wavelength.
You are welcome! It is a pretty common misunderstanding for electromagnetic waves just because of the way books draw EM waves.
 
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  • #9
Dale said:
You are welcome! It is a pretty common misunderstanding for electromagnetic waves just because of the way books draw EM waves.
you are totally right! for ex. one can easily conclude from the way pictures represent them (particulary, basic wave function) that T[period]=lambda[wavelength], which at first seems very obvious and unit-wise not.
 

1. Why is the arc length formula not used to calculate wavelength?

The arc length formula, s = rθ, is used to calculate the length of a circular arc. However, the wavelength of a wave is not a circular arc and does not have a defined radius or central angle. Therefore, this formula is not applicable to calculate wavelength.

2. How is wavelength calculated instead of using the arc length formula?

Wavelength is calculated using the formula λ = v/f, where λ represents wavelength, v represents wave velocity, and f represents frequency. This formula is derived from the relationship between wavelength, frequency, and wave velocity in the wave equation, c = fλ, where c is the speed of light.

3. Can the arc length formula be used to calculate the wavelength of a circular wave?

No, the arc length formula cannot be used to calculate the wavelength of a circular wave because the formula calculates the length of a circular arc, not the distance between two points on the circumference of the circle.

4. Is the arc length formula used in any other scientific calculations?

Yes, the arc length formula is commonly used in geometry and trigonometry to calculate the length of a circular arc, as well as in physics to determine the displacement of an object moving in a circular motion. However, it is not applicable to calculate the wavelength of a wave.

5. Why is it important to use the correct formula to calculate wavelength?

Using the correct formula to calculate wavelength is important because it ensures accurate and precise measurements. The arc length formula is not applicable to calculate wavelength, and using it would result in incorrect values. By using the correct formula, scientists can obtain reliable data and make accurate conclusions in their research.

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