Super199
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Can someone explain part e for me.

the sound one is the speakers I tthink the microwave one is where you have a transmitter and a receiver and you move the receiver parallel to the transmitter. There are sheets of metal to cause the diffraction I think. Is the light one young double slit?

Also if it is what is the difference between that and point h and j as well. Can someone clarify which experiments are for each point?

thanks
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LibertyMan
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There is no diffraction involved with Microwaves... you just move the transmitters.

The light one is young's double slit, yes.

The difference is at e) they want you to talk about wave interference, in h) they want you to talk about how the experiement shows light is a wave (and you can use the argument about interference, but you might want to check in a mark scheme for that) and j) is about using the diffraction grating or double slit for working out the wavelength of the light based on the formulae.
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Super199
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(Original post by LibertyMan)
There is no diffraction involved with Microwaves... you just move the transmitters.

The light one is young's double slit, yes.

The difference is at e) they want you to talk about wave interference, in h) they want you to talk about how the experiement shows light is a wave (and you can use the argument about interference, but you might want to check in a mark scheme for that) and j) is about using the diffraction grating or double slit for working out the wavelength of the light based on the formulae.
Just to clarify point h. If light was a particle it would mean you would get two distinctive lines. Not 100% sure about how it proves that it shows light is a wave. Is it because as it passes through the slit (similar size to it's wavelength) it spreads out (diffracts). As there are two slits two rays will be diffracted. We will get constructive and destructive interference. The constructive interference is when they have a path difference of a whole wavelength and half with destructive. Constructive interference are the bright spots. It would be appreciated if you could tell me if I have missed something or if I have misunderstood something. Thanks
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LibertyMan
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Yep. We would expect 2 coherent waves to 1) diffract when they pass through a gap each and 2) create the interference pattern because of constructive and destructive interference. This shows light is a wave as only a wave would behave like this- diffraction and interference are both wave properties.

(Original post by Super199)
As there are two slits two rays will be diffracted.
Well, each slit has it's own ray- there is a single source which is split first by 1 slit, so they spread equally in all directions, and then by the 2 slits from the experiement. This is so light is coherent (they sometimes ask why only 1 source is used and thats the answer).


Image


You also understand WHY a path difference of 1 wavelength is constructive and that of a 1/2 is destructive, yes?
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Super199
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(Original post by LibertyMan)
Yep. We would expect 2 coherent waves to 1) diffract when they pass through a gap each and 2) create the interference pattern because of constructive and destructive interference. This shows light is a wave as only a wave would behave like this- diffraction and interference are both wave properties.



Well, each slit has it's own ray- there is a single source which is split first by 1 slit, so they spread equally in all directions, and then by the 2 slits from the experiement. This is so light is coherent (they sometimes ask why only 1 source is used and thats the answer).


Image


You also understand WHY a path difference of 1 wavelength is constructive and that of a 1/2 is destructive, yes?
Not entirely. I have just accepted that fact? What is the reasoning behind it?
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LibertyMan
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(Original post by Super199)
Not entirely. I have just accepted that fact? What is the reasoning behind it?
The resultant wave from 2 or more waves being in superposition is simply the sum of their displacements.

Image

Every wavelength apart the 2 displacements are at equal signs (up being positive and down negative) and are maximum, so they will create the biggest resultant displacement both up and down.

Every half, the 2 displacements are at their maximum but the signs are opposite, so they cancel out.

Only reason I asked was because knowing this fact makes the rest easier to understand.
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Super199
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(Original post by LibertyMan)
The resultant wave from 2 or more waves being in superposition is simply the sum of their displacements.

Image

Every wavelength apart the 2 displacements are at equal signs (up being positive and down negative) and are maximum, so they will create the biggest resultant displacement both up and down.

Every half, the 2 displacements are at their maximum but the signs are opposite, so they cancel out.

Only reason I asked was because knowing this fact makes the rest easier to understand.
Got it! Cheers
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