Young's double slit and coherent light

In summary, the textbook discusses the occurrence of constructive and destructive interference at path differences of m \lambda and (m + 1/2) \lambda, respectively, where m is an integer. While it is commonly believed that the waves must be in phase for this to happen, the book clarifies that coherence, or a constant phase difference, is actually the determining factor. This means that even if the waves are not in phase at the two slits, they can still produce a fringe pattern.
  • #1
sorax123
34
0
Hello all,
I was looking through my textbook on the double slit and it talks about constructive interference occurring at path differences of m [itex]\lambda[/itex] and destructive interference occurring at path differences of (m + 1/2) [itex]\lambda[/itex] where m is an integer. This is obvious if the waves leave the 2 slits in phase, however the book states that it is not necessary for the waves to be in phase, just for them to be coherent (ie. constant phase difference). Now I understand how the fringe pattern would form here but I fail to understand how the above conditions can be true as for the two to be in phase, one would have to travel further to be in phase at the arbitrary point P. Is this a textbook oversight or am I missing something?
Thanks,
Dom
 
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  • #2
If the incoming light has different phases at the slits, the points of constructive/destructive interference will be different as well, right.
 
  • #3
So the constructive interference only occurs at m [itex]\lambda[/itex] if in phase at the slits as I assumed?
 
  • #5
I see, thanks very much for clearing that up.
 

FAQ: Young's double slit and coherent light

What is Young's double slit experiment?

Young's double slit experiment is a classic experiment in optics that demonstrates the wave nature of light. It involves shining a coherent light source, such as a laser, through two narrow slits and observing the resulting interference pattern on a screen. This experiment was first conducted by Thomas Young in the early 1800s and has since been replicated and studied extensively.

What is coherent light?

Coherent light is light that has a constant phase relationship between its waves. In other words, all the waves are in sync and have the same frequency and wavelength. This is typically achieved using a laser, where the light is produced by stimulated emission, resulting in a highly coherent beam.

How does Young's double slit experiment demonstrate the wave nature of light?

In Young's double slit experiment, the light passing through the two slits diffracts and creates a pattern of bright and dark fringes on the screen. This can only be explained by the interference of the waves, which is a characteristic behavior of waves. If light behaved solely as particles, as was previously believed, there would be no interference pattern observed.

What factors affect the interference pattern in Young's double slit experiment?

The interference pattern in Young's double slit experiment is affected by several factors, including the distance between the slits, the distance between the slits and the screen, and the wavelength of the light used. Additionally, the pattern can also be affected by the size and shape of the slits, as well as any obstructions or imperfections in the setup.

What other phenomena can be explained using the principles of Young's double slit experiment?

The principles of Young's double slit experiment have been applied to other phenomena, such as the diffraction of light through a single slit and the interference of water waves. The concept of interference is also used in other fields, such as acoustics and quantum mechanics, to explain various behaviors of waves and particles.

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