Interference and diffraction of light

In summary: What's the academy award about Brando :tongue2:What's the academy award about Brando :tongue2:In summary, two incandescent globes can't be observed to produce an interference pattern because they have no coherent light.
  • #1
chisai_tam
1
0
Why is it impossible to observe an interference pattern from two adjacent incandescent globes?

What is meant by coherant light- and how would you describe two ways of producing it?
 
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  • #2
chisai_tam said:
Why is it impossible to observe an interference pattern from two adjacent incandescent globes?

What is meant by coherant light- and how would you describe two ways of producing it?


Coherent light can be defiened intuitively as very ordened and structured light. I mean than the wave representing the light does not really change it's properties like fasedifferences with respect to other lightwaves e.a.

The best known example is the laser.

An Incoherent lightsource has no order, this means that the waves propagate in different directions with all kinds of phasedifferences between the various waves. Coherent sources like the laser-resonator make sure that you get one light-wave-packet that is very ordened. All the constituant waves that make up the laser-light all vibrate in the same way, with the same constant phase-differences with respect to each other.


I don't get your first question though ? What do you mean

regards
marlon
 
  • #3
I think chisai_tam meant : why no interference form two different sources ? If this is the case, you answered already : two different sources cannot be coherent.

By the way : welcome to you chisai_tam.
 
  • #4
humanino said:
I think chisai_tam meant : why no interference form two different sources ? If this is the case, you answered already : two different sources cannot be coherent.

By the way : welcome to you chisai_tam.


True story, shuman, eeuhh, i mean humanino. Forgot you want to be a boson-like character , meating as much superpartners as possible at once...

regards
marlon, two times academy-award-winner
 
  • #5
What's the academy award about Brando :-p
 
  • #6
humanino said:
What's the academy award about Brando :-p


What do you mean ?

Brando won two oscars for Over the Waterfront and The Godfather

regads
marlon corleone
 
  • #7
"Coherent" light is light that consists of one specific wave length (in practice, a limited range of frequency). For example, burning salt produces a "yellow" flame because almost all of the light produced is in a narrow range of "yellow" frequencies.
A "neon" light will produce light in the spectrum of neon- still fairly limited.

In order to see interference (over more than, say, a millionth of a second!) you must have two waves of the frequency but slightly out of phase. Having light of many different wave lengths will obscure the phenomenon.
 
  • #8
Yes he did. I was teasing you. I like too this great actor. Did not he die recently by the way :rolleyes:

pacino :biggrin:
 
  • #9
HallsofIvy said:
"Coherent" light is light that consists of one specific wave length (in practice, a limited range of frequency)

I am not certain this is very accurate Hallsoflvy. I think the well-defined wavelength is necessary. But still, you cannot make two different laser at the same color interfere. The coherence is
1 in time
2 in space

A coherent source emits bunchs of light, with a certain time and space extension. If for instance you separate a laser light in two beams, and try to make interferences, you cannot have a too large difference between the two paths, because that would spoil time coherence.
 
  • #10
wikipedia will tell it better than I do.
 
  • #11
HallsofIvy said:
"Coherent" light is light that consists of one specific wave length (in practice, a limited range of frequency). For example, burning salt produces a "yellow" flame because almost all of the light produced is in a narrow range of "yellow" frequencies.
A "neon" light will produce light in the spectrum of neon- still fairly limited.

In order to see interference (over more than, say, a millionth of a second!) you must have two waves of the frequency but slightly out of phase. Having light of many different wave lengths will obscure the phenomenon.


I also think this is wrong.

You are mixing things up. You are referring to monochromatic-light...
You don't need light that is completely monochromatic in order for it to be coherent.

Indeed, Wikipedia gives a nice review of the different types of coherence.


regards
marlon
 
Last edited:
  • #12
Yes, I also believe monochromaticity is not required. Although, the coherent sources I know are all monochromatic.
EDIT : so I was wrong when I said "well-defined wavelength is necessary"
 
  • #13
Brando passed away on the first of july 2004, the day of my last exam !

This is not coincidence !


regards
marlon
 

FAQ: Interference and diffraction of light

What is the difference between interference and diffraction of light?

Interference refers to the phenomenon where two or more light waves interact with each other and either amplify or cancel each other out, resulting in a pattern of bright and dark fringes. Diffraction, on the other hand, is the bending of light waves around obstacles or through narrow openings, resulting in a spreading out of the light. Both interference and diffraction are caused by the wave nature of light.

What types of waves can undergo interference and diffraction?

Interference and diffraction can occur with any type of wave, including light waves, sound waves, and water waves. However, the specific patterns and behaviors may vary depending on the type of wave and the medium through which it is traveling.

How does the wavelength of light affect interference and diffraction?

The wavelength of light is directly related to the spacing of the fringes in an interference pattern and the amount of diffraction that occurs. Shorter wavelengths, such as blue and violet light, will result in more closely spaced fringes and more pronounced diffraction effects, while longer wavelengths, such as red and orange light, will have wider spaced fringes and less diffraction.

Can interference and diffraction occur with only one light source?

Yes, interference and diffraction can still occur with a single source of light, as long as the light passes through a narrow slit or around an obstacle. In this case, the light waves will interfere with each other or diffract as they pass through the opening, resulting in a pattern of bright and dark fringes.

What are some practical applications of interference and diffraction of light?

The study of interference and diffraction has many practical applications, including in the fields of optics, microscopy, and spectroscopy. It is also used in technologies such as holography, fiber optics, and diffraction gratings. In addition, the patterns and colors created by interference and diffraction can be seen in everyday objects, such as soap bubbles and oil slicks.

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