Red Fringe Count in Young's Double Slit Experiment

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In summary, in a Young's double slit experiment, blue monochromatic light of wavelength 450nm is used to illuminate the slits which are 0.60mm apart. A screen is placed 1.5m from the slit to catch the interference pattern. The question asks how many fringes will be seen if red light with a wavelength of 700nm is used, and the answer is 7. The equation used is dsinθ = mλ, and the concept of calculating the maximum order of fringes is used. However, the question may be incomplete or mixed-up as the relevance of the blue light is unclear and the exact dimensions of the screen are not specified.
  • #1
somecelxis
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Homework Statement



In a Young's double slit experiment , blue monochromatic light of wavelength 450nm is used to illuminate the slits which are 0.60mm apart. A screen is placed 1.5m form the slit is used to catch the interfrence pattern .
If red light is used (700nm) , how many red light will be seen? the ans is 7

Homework Equations





The Attempt at a Solution


dsinθ = m λ
0.6x10^-3 ( sin 90 ) = m (700x10^-9)
m = 857
no fringe can be seen = 857+ 857+1 ..
What's wrong with my working?
 
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  • #2
where does sin(90) come from?
 
  • #3
Sin90 beacuse I wamt to calculate themaximum order of fringes. Is my concept wrong?
 
  • #4
no fringe can be seen = 857+ 857+1 ..
What's wrong with my working?
I would agree with you. Perhaps the question is meant to say something like "a 1 metre square screen is placed 1.5m from the slits".

Can you work backwards, and work out what screen dimension would show just 7 bands either side of the central maximum?
 
  • #5
Do you meam the fringe is only formed on 1mm square of screen?
 
  • #6
somecelxis said:
Do you meam the fringe is only formed on 1mm square of screen?
If you were wanting to see just the first order fringe, yes, that might be about right. But didn't you say the answer is n=7?

Could you check the question, and make sure you haven't got some detail wrong.
 
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  • #7
How is the part about blue light relevant? It seems that the question is incomplete or mixed-up somehow.
 
  • #8
NascentOxygen said:
I would agree with you. Perhaps the question is meant to say something like "a 1 metre square screen is placed 1.5m from the slits".

Can you work backwards, and work out what screen dimension would show just 7 bands either side of the central maximum?

that's the whole question i have typed above...
 

1. What is the phenomenon of "No of red fringe will be seen"?

The phenomenon of "No of red fringe will be seen" is known as the interference of light waves. When two or more light waves overlap, they interfere with each other, resulting in the formation of bright and dark fringes. The number of red fringes seen depends on the wavelength of the light and the distance between the light source and the observer.

2. How is the number of red fringes seen related to the wavelength of light?

The number of red fringes seen is directly proportional to the wavelength of light. This means that as the wavelength of light increases, the number of red fringes seen also increases. This is because longer wavelengths of light diffract more, resulting in more interference patterns and thus, more red fringes.

3. Can the number of red fringes seen be influenced by the distance between the light source and the observer?

Yes, the number of red fringes seen can be influenced by the distance between the light source and the observer. As the distance increases, the angle of diffraction also increases, resulting in a larger number of red fringes being observed. This is why the number of red fringes seen may vary when observing the same light source from different distances.

4. What factors can affect the visibility of red fringes?

There are several factors that can affect the visibility of red fringes, including the intensity and direction of the light source, the distance between the light source and the observer, and the clarity of the medium through which the light is passing. Other factors such as the angle of incidence and the properties of the light-sensing equipment may also play a role.

5. Is the number of red fringes seen always the same for a given light source?

No, the number of red fringes seen can vary for a given light source depending on the factors mentioned above. Additionally, if the properties of the light source, such as its wavelength or intensity, change, the number of red fringes observed may also change. This is why it is important to control and account for these factors when studying the interference of light waves.

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