Timeline for Why does wavelength affect diffraction?
Current License: CC BY-SA 3.0
16 events
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| Sep 21, 2018 at 3:38 | comment | added | Kentzo | Please correct me if I'm wrong, but I found it more intuitive to understand magnitude of diffraction in terms of constructive and deconstructive interference. Bigger slit for the same wavelength -> more deconstructive interferences. Longer wavelength for the same slit -> fewer constructive interferences | |
| Jul 14, 2014 at 11:44 | comment | added | Phil Frost | @rahulgarg12342 it doesn't change the delay, in time or distance. It changes the delay in phase. If wavelength is 1000nm and you are 500nm away, that's a 180 degree phase delay. If wavelength is 2000nm (and you are still 500nm away) that's a 90 degree phase delay. longer wavelength -> lower frequency -> phase changing more slowly -> longer distance required for identical phase delay. | |
| Jul 14, 2014 at 11:35 | comment | added | rahulgarg12342 | That makes sense. But after thinking a lot, how would a change in wavelength cause more delay? Isn't the speed of light the same. Or less frequency causes more delay. Is my thinking right? | |
| Jul 14, 2014 at 11:34 | vote | accept | rahulgarg12342 | ||
| Jul 14, 2014 at 11:04 | comment | added | Phil Frost | @rahulgarg12342 yes, that is the right line of thinking. Stop thinking about angles and bending. Light doesn't "bend" because it's a wave, not a ray (and if you want to get all quantumy then it's also a particle, but not one that travels in simple straight lines). Think about how distance introduces a phase delay, and that delay is proportional to the distance and the wavelength. Then think about how if the phase from two sources is the same they add, and if the phases are opposite, they cancel. For a simpler case, maybe read about phased antenna arrays. | |
| Jul 14, 2014 at 5:11 | comment | added | rahulgarg12342 | @PhilFrost I tried imagining the images scaled and the angle still seems the same to me. Is it something like that when the wavelength gets bigger, then the waves interfere at a greater distance? | |
| Jul 13, 2014 at 13:14 | comment | added | Phil Frost | @rahulgarg12342 can you imagine taking any of these images and scaling them in size? You have a bigger slit, and a longer wavelength if you make them bigger, but the pattern is the same. But what if you want to change the wavelength but not the slit? You could scale the image (increasing the wavelength and making the slit bigger) then make the slit smaller (so it's the same size it was before scaling). | |
| Jul 13, 2014 at 12:44 | comment | added | rahulgarg12342 | But how will that affect the distance of interference and the angle of diffraction? The only part I don't understand is how making the wavelength smaller is equivalent to making the slit size bigger. | |
| Jul 13, 2014 at 10:58 | comment | added | Phil Frost | @rahulgarg12342 wavelength and frequency are two ways to express the same thing: how fast the wave changes. A longer wavelength has a lower frequency: it oscillates more slowly. A shorter wavelength has a higher frequency: it oscillates more quickly. | |
| Jul 13, 2014 at 10:35 | comment | added | rahulgarg12342 | I understood everything very well except the last part where you say that the rate of change in wave function is faster. Can you please explain what did you exactly mean by the rate of change in wave function is faster? Thanks. | |
| Jul 11, 2014 at 14:17 | comment | added | sailx | Nice answer. maube it's interresting to give a adimensionned number. I think of the Fresnel number : en.wikipedia.org/wiki/Fresnel_number. If you take the same F-number, you will have the same propertie up to an homothetie. | |
| Jul 11, 2014 at 13:45 | comment | added | Mike M | I think this is an awesome answer, for what the OP is trying to get at and in detail. | |
| Jul 11, 2014 at 7:57 | comment | added | gatsu | @romkyns: for diversity I suppose....Besides, the physics of waves might not be (and doesn't have to be) appealing to everybody. | |
| Jul 10, 2014 at 19:34 | history | edited | Phil Frost | CC BY-SA 3.0 |
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| Jul 10, 2014 at 19:15 | comment | added | Roman Starkov | +1; why does everyone else go into QED and path integrals when the answer applies to classical waves just the same? | |
| Jul 10, 2014 at 18:45 | history | answered | Phil Frost | CC BY-SA 3.0 |