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Young double slit experiment

  • #1
hello,

i am doing a work sheet on the title of this thread and i do not have the answer sheet for the questions so can some one please go through my answers and see if i am correct

Young used a monochromatic light source
a) wat does this mean?
my ans: light of a single wavelength

b) how did he achieve this?
my ans: by using sunlight

c)wat is the purpose of the single slit?
my ans: so that only light from the single slit will reach the double slit

d)when does destructive interference occur?
when the wavelength is 1/2 of the wavelength of the bright fringes
 

Answers and Replies

  • #2
Doc Al
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Ukitake Jyuushirou said:
Young used a monochromatic light source
a) wat does this mean?
my ans: light of a single wavelength
That's the correct meaning of monochromatic.

b) how did he achieve this?
my ans: by using sunlight
Sunlight is not monochromatic.

c)wat is the purpose of the single slit?
my ans: so that only light from the single slit will reach the double slit
Well, yes, but why is that important? (The key is that it keeps the path length the same for light hitting the double slits.)

d)when does destructive interference occur?
when the wavelength is 1/2 of the wavelength of the bright fringes
Not sure what that means. Hint: What must be the path length difference between light from each slit arriving at a point on the screen so that there is destructive interference?
 
  • #3
thank u doc

for the qn 2 , wat then qualifies as a monochromatic light?

for the last qn, i mean to say the path difference between the 2 sources must be 1/2 wavelength
 
  • #4
Doc Al
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Ukitake Jyuushirou said:
for the qn 2 , wat then qualifies as a monochromatic light?
I don't know what Young did in his orginal experiments to get a monochromatic source, but he could have used a filter or a prism to select a single wavelength. (If you don't use a monochromatic source, then you'll get overlapping fringes from each wavelength.) Nowadays, getting a monochromatic source is easy using lasers.

for the last qn, i mean to say the path difference between the 2 sources must be 1/2 wavelength
Good. The path difference of the light from each slit must be 1/2 wavelength for destructive interference.
 
  • #5
Doc Al said:
I don't know what Young did in his orginal experiments to get a monochromatic source, but he could have used a filter or a prism to select a single wavelength. (If you don't use a monochromatic source, then you'll get overlapping fringes from each wavelength.) Nowadays, getting a monochromatic source is easy using lasers.
Good. The path difference of the light from each slit must be 1/2 wavelength for destructive interference.
I assume he used a sodium lamp - it's monochromatic enough (not coherent though - that doesn't mean it's impossible to do but it makes it bl--dy hard (speaking from experience here :cry: )
 
  • #6
brewnog
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I believe Young did use sunlight in his original experiment.
 
  • #7
Doc Al
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brewnog said:
I believe Young did use sunlight in his original experiment.
Absolutely. I just don't know what pains, if any, he took to select a particular wavelength.
 

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