Interference Pattern: Non-Laser Light Sources

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Discussion Overview

The discussion revolves around the feasibility of performing the double slit experiment using non-laser light sources to observe interference patterns. Participants explore various types of light and methods for achieving collimation and coherence necessary for the experiment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the light used in the double slit experiment need not be chromatic, while others clarify that coherence is essential for observing interference patterns.
  • One participant suggests that collimating light through narrow gaps can help achieve the necessary conditions for interference, mentioning the use of a battery torch and the challenges of visibility in a lit environment.
  • Another participant emphasizes that while interference can occur with non-monochromatic light, the resulting patterns may overlap and be harder to discern.
  • A later reply discusses the use of a semi-transparent diffuser screen to enhance visibility of the interference pattern, detailing specific dimensions and light sources used in their setup.
  • Some participants argue that any light emitted from the same source is coherent enough to produce interference patterns, suggesting sunlight or flashlights as viable options, although LEDs may provide better results due to uniformity.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of coherence and monochromaticity in achieving observable interference patterns. There is no consensus on the best light source or method for performing the experiment without lasers.

Contextual Notes

Participants mention practical challenges such as the need for a dark room and the difficulty in blocking stray light, which may affect the visibility of the interference pattern.

Quantumgravity
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Is there any way to perform the double slit experiment and see the interference pattern without using a laser? If so, what type of light do you need?
 
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As far as I understand it- the light need not be chromatic at all.
 
christianjb said:
As far as I understand it- the light need not be chromatic at all.
What do you mean by chromatic?

As for how to do it.. collimate the light by letting it pass through a very narrow gap (say, between two razor blades). Then have it go through another such gap, or your double slit perhaps. You may need some kind of lens to appreciate the pattern. Works fine with a normal battery torch.. well.. actually it's a pain because you likely need a dark room to be able to see the small amount of light involved, and you need to block out the extra torchlight.. it's fiddly.
 
Sorry- I meant coherent. It may have to be reasonably monochromatic in order to see interference.
 
The interference will occur even if the light is not monochromatic, but of course all the patterns will overlap and mix and the overall pattern, whilst still there, will be more difficult to see.
 
It does have to be coherent though, which is the reason for the collimation. :wink:
 
cesiumfrog said:
As for how to do it.. collimate the light by letting it pass through a very narrow gap (say, between two razor blades). Then have it go through another such gap, or your double slit perhaps. You may need some kind of lens to appreciate the pattern. Works fine with a normal battery torch.. well.. actually it's a pain because you likely need a dark room to be able to see the small amount of light involved, and you need to block out the extra torchlight.. it's fiddly.

Right. We do it by using a semi-transparent "diffuser" screen as the final target, and looking at the back side, in the direction of the slits and the light source. If you turn out the room lights and block stray light from the source, you can easily get a dim but clearly visible interference pattern that's perhaps a centimeter wide. Our initial collimating slit is 0.1 mm wide, and we use a small high-intensity desk lamp as the light source, with a clear-glass bulb so the filament makes for a fairly small source already.
 
Thanks for the input.
 
actually any light that has been emitted by the same source is coherent, so you can get an interference pattern using sunlight and or a flashlight. however an led would be better as there would be fewer differences over the emitter surface.
 

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