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April 29, 2024, 06:02:54 pm
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Author Topic: Diffraction ratios?  (Read 5589 times)  Share 

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Linkage1992

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Diffraction ratios?
« on: November 09, 2010, 07:09:43 pm »
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I always get screwed over on these questions because I never know how far their interpretation of "approximately equal to 1" for significant diffraction is.

For instance, in vcaa 2007 i said that because the ratio was 1: 1.5, which I think is a fairly large deviation, there would not be significant diffraction, but the answers say there is. How far are you supposed to go??
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kyzoo

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Re: Diffraction ratios?
« Reply #1 on: November 09, 2010, 07:12:05 pm »
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lol after getting screwed over by these kidns of questions, I just go with the rule "of wavelength/length >0.1", then significant diffraction occurs. It's better than >1 because you have these stupid questions where its ":same order of magnitude"

Significant diffraction occurs when either 1.) wavelength is on the same order of magnitude as the gap 2.) wavelength is much bigger than the gap.
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Linkage1992

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Re: Diffraction ratios?
« Reply #2 on: November 09, 2010, 07:15:19 pm »
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okay, so when you have two values to, say, the power of -10, chances are they'll always expect you to put significant diffraction?
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Chavi

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Re: Diffraction ratios?
« Reply #3 on: November 09, 2010, 07:15:27 pm »
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λ/w>1 so λ>w
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3Xamz

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Re: Diffraction ratios?
« Reply #4 on: November 09, 2010, 07:19:11 pm »
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If its greater than by 1 order = lot of diffraction
If its the same order = some diffraction
If its less than by 1 order = no diffraction.

Hence for wavelength/gap;
1) 1 or more = lot of diffraction
2) between 0.1 to 0.9 - some diffraction
3) <0.1 - no diffraction.
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lachymm

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Re: Diffraction ratios?
« Reply #5 on: November 09, 2010, 07:20:51 pm »
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I just use a ratio of .1 to 10...Lamda doesnt have to be greater than or equal to width...significant diffraction occurs when the width is greater than the wavelength...
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3Xamz

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Re: Diffraction ratios?
« Reply #6 on: November 09, 2010, 07:22:18 pm »
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Quote from: lachymm on November 09, 2010, 07:20:51 pm
I just use a ratio of .1 to 10...Lamda doesnt have to be greater than or equal to width...significant diffraction occurs when the width is greater than the wavelength...

That sir, is not true.
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Chavi

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Re: Diffraction ratios?
« Reply #7 on: November 09, 2010, 07:23:15 pm »
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Quote from: lachymm on November 09, 2010, 07:20:51 pm
I just use a ratio of .1 to 10...Lamda doesnt have to be greater than or equal to width...significant diffraction occurs when the width is greater than the wavelength...
other way around
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TyErd

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Re: Diffraction ratios?
« Reply #8 on: November 09, 2010, 08:51:40 pm »
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if slit width is much smaller than the wavelength, that would mean there's a lot of diffraction right?
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Chavi

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Re: Diffraction ratios?
« Reply #9 on: November 09, 2010, 08:53:02 pm »
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Quote from: TyErd on November 09, 2010, 08:51:40 pm
if slit width is much smaller than the wavelength, that would mean there's a lot of diffraction right?
yepp. Just remember that diffraction occurs when λ>w
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TyErd

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Re: Diffraction ratios?
« Reply #10 on: November 09, 2010, 09:07:42 pm »
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umm question 2 the solutions says the answer is B but isn't it D?
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TyErd

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Re: Diffraction ratios?
« Reply #11 on: November 09, 2010, 09:12:51 pm »
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but slit width is smaller than wavelength
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superflya

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Re: Diffraction ratios?
« Reply #12 on: November 09, 2010, 09:13:15 pm »
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its more significant when the value of the ratio is ~1.
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TyErd

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Re: Diffraction ratios?
« Reply #13 on: November 09, 2010, 09:17:21 pm »
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isn't it more significant when it is greater than 1?
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waack

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Re: Diffraction ratios?
« Reply #14 on: November 09, 2010, 09:20:22 pm »
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significant diffraction occurs when the width of the gap and the wavelength are of the same order simple as that, if both are any number x 10^-6 ie same order it will occur if it is ~ 1 then yes it will occur
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