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March 29, 2024, 04:49:21 am

Author Topic: Diffraction ratios?  (Read 5533 times)  Share 

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TyErd

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Re: Diffraction ratios?
« Reply #15 on: November 09, 2010, 09:25:51 pm »
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so what happens if it is greater than 1? diffraction decreases?
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waack

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Re: Diffraction ratios?
« Reply #16 on: November 09, 2010, 09:40:42 pm »
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i asked teacher about this one and apprently it gets complicated and uni level stuff he said its very unlikely to occur and he knows the statistics for vcaa for the last 30 years and 20 years of hsc before that i trust him

m@tty

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Re: Diffraction ratios?
« Reply #17 on: November 09, 2010, 09:46:39 pm »
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λ/w>1 so λ>w

The 2007 VCAA question said that a slit of width will create significant diffraction with neutrons of wavelength . They claimed that they were "of the same magnitude" and a diffraction pattern would form.

So obviously we can't rely on the rule.
« Last Edit: November 09, 2010, 09:54:50 pm by m@tty »
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TyErd

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Re: Diffraction ratios?
« Reply #18 on: November 09, 2010, 09:50:10 pm »
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0.667 is pretty close to 1 so okay that's settled i guess, for significant diffraction has to be approximately 1, not greater
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fady_22

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Re: Diffraction ratios?
« Reply #19 on: November 09, 2010, 09:51:59 pm »
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0.667 is pretty close to 1 so okay that's settled i guess, for significant diffraction has to be approximately 1, not greater

No, significant diffraction occurs when the ratio is greater than 1, however it is maximised when it is approximately equal to one.
Thats how I understand it, anyway.
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waack

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Re: Diffraction ratios?
« Reply #20 on: November 09, 2010, 09:54:27 pm »
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λ/w>1 so λ>w

The 2007 VCAA question said that a slit of width will create significant diffraction with neutrons of wavelength . They claimed that they were "of the same magnitude" and a diffraction pattern would form.
it says same 'order of magnitude' so when u convert the width and wavelength to m x 10^- (number) if the order being the number is the same for both in m then diffraction will be significant

So obviously we can't rely on the rule.
it actually says same magtitude of order which means when u convert the width of the gap and the wavelegth to m x 10^- (whatever number) if the number is the same for both they are of the same order and significant diffraction will occur
« Last Edit: November 09, 2010, 09:56:24 pm by waack »

Munkea

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Re: Diffraction ratios?
« Reply #21 on: November 09, 2010, 09:54:33 pm »
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0.667 is pretty close to 1 so okay that's settled i guess, for significant diffraction has to be approximately 1, not greater

No, significant diffraction occurs when the ratio is greater than 1, however it is maximised when it is approximately equal to one.
Thats how I understand it, anyway.
Not true, significant diffraction occurs when the ratio is approximately 1. For a value such as 0.6, significant diffraction would occur.

fady_22

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Re: Diffraction ratios?
« Reply #22 on: November 09, 2010, 09:55:41 pm »
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I meant significant diffraction occurs when it is greater than or approximately equal to one.
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m@tty

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Re: Diffraction ratios?
« Reply #23 on: November 09, 2010, 09:56:38 pm »
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So then, do we go by the "of the same order" approach?

Significant diffraction will occur if ?? ??
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TyErd

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Re: Diffraction ratios?
« Reply #24 on: November 09, 2010, 10:09:44 pm »
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argh im confused again. Whats the difference between maximized and significant diffraction?
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Ovalteenies

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Re: Diffraction ratios?
« Reply #25 on: November 09, 2010, 10:13:52 pm »
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So basically diffraction is significant for
but is maximised at 1

fady_22

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Re: Diffraction ratios?
« Reply #26 on: November 09, 2010, 10:15:49 pm »
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Since this ratio determines the spacing of the individual fringes, it determines the width of the overall diffraction pattern. The diffraction pattern will have a central fringe that is twice as wide as the other fringes. If the wavelength is held constant and the aperture or gap is made smaller, greater diffraction is seen. If different wavelengths enter the same gap, those with a small wavelength will undergo less diffraction than those with longer wavelengths. For example, the use of an aperture of a given width will result in greater diffraction of red light than blue light just as occurred with double-slit diffraction (Figure 11.15). Do not think of diffraction effects as suddenly occurring at a specific wavelength. Although we need λ ≈ w for a good diffraction pattern, diffraction will gradually increase if the values of λ and w are made to gradually approach one another.

Taken from the Heinemann book.
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waack

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Re: Diffraction ratios?
« Reply #27 on: November 09, 2010, 10:16:16 pm »
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pretty much^^

TyErd

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Re: Diffraction ratios?
« Reply #28 on: November 09, 2010, 10:18:24 pm »
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Since this ratio determines the spacing of the individual fringes, it determines the width of the overall diffraction pattern. The diffraction pattern will have a central fringe that is twice as wide as the other fringes. If the wavelength is held constant and the aperture or gap is made smaller, greater diffraction is seen. If different wavelengths enter the same gap, those with a small wavelength will undergo less diffraction than those with longer wavelengths. For example, the use of an aperture of a given width will result in greater diffraction of red light than blue light just as occurred with double-slit diffraction (Figure 11.15). Do not think of diffraction effects as suddenly occurring at a specific wavelength. Although we need λ ≈ w for a good diffraction pattern, diffraction will gradually increase if the values of λ and w are made to gradually approach one another.

Taken from the Heinemann book.


okay so that's maximised diffraction. What about significant diffraction?
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fady_22

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Re: Diffraction ratios?
« Reply #29 on: November 09, 2010, 10:19:40 pm »
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Go with the "same order" definition.
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