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Edexcel Physics Unit 2 "Physics at work" June 2013

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Original post by Munchee
Can someone please tell me the equation to calculate path difference from phase difference? And the equations derived from the doppler effect, asap would be awesome :biggrin:


Path difference = n*lambda When constructive Interference occurs
Path difference = (2n+1)*lambda/2

There isn't really an equation for phase difference. But Pi=lambda/2
Reply 541
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LegendX
15
Original post by CharlieTT
Path difference = n*lambda When constructive Interference occurs
Path difference = (2n+1)*lambda/2

There isn't really an equation for phase difference. But Pi=lambda/2


Is there any way to remember the wavelengths of EM waves? Also, how do you know which LED is what wavelength in the jan 2009 paper question 21? Thanks
Reply 542
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vinhvu95
Original post by LegendX
Is there any way to remember the wavelengths of EM waves? Also, how do you know which LED is what wavelength in the jan 2009 paper question 21? Thanks


You don't need to remember them, just remember which waves have a higher frequency e.g. Ultraviolet has a higher frequency than radio waves, in the LED question they gave you the set of data which you need to examine


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Reply 543
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LegendX
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Original post by vinhvu95
You don't need to remember them, just remember which waves have a higher frequency e.g. Ultraviolet has a higher frequency than radio waves, in the LED question they gave you the set of data which you need to examine


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I understand that ultraviolet has higher frequency than radio waves but how does this relate to colour? :smile:
Original post by LegendX
Is there any way to remember the wavelengths of EM waves? Also, how do you know which LED is what wavelength in the jan 2009 paper question 21? Thanks


1 - Green
2 - Orange
3 - Red

E=hf
=6.63x10^(-34)Js*4.41x10^(14)Hz
=2.924x10^(-19)J

You don't need to remember exact wavelengths that'd be silly. Just remember the order they go in from Large to small. Radio, Micro, Infrared, Visible, UltraViolet, X, Gamma.
(edited 10 years ago)
Reply 545
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LegendX
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Original post by CharlieTT
1 - Green
2 - Orange
3 - Red

E=hf
=6.63x10^(-34)Js*4.41x10^(14)Hz
=2.924x10^(-19)J

You don't need to remember exact wavelengths that'd be silly. Just remember the order they go in from Large to small. Radio, Micro, Infrared, Visible, UltraViolet, X, Gamma.


I can do the calculation but how do you know what colour they are? :confused:
Reply 546
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Munchee
6
Original post by CharlieTT
Path difference = n*lambda When constructive Interference occurs
Path difference = (2n+1)*lambda/2

There isn't really an equation for phase difference. But Pi=lambda/2


Thank you!
Can someone please tell me why the answer to question 9 June 2010 is C? Im so confused :frown:
Original post by LegendX
I understand that ultraviolet has higher frequency than radio waves but how does this relate to colour? :smile:


yeah so just think red is close to infraRED and so has higher wavelength/lower frequency compared to violet in the visible light spectrum which is closer to Ultra VIOLET. And obviously orange would be in between.
Reply 549
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Jaydude
11
I read refractive index for light passing through any medium must be greater than 1. (Due to speed of light in vacuum cant exceed 3*10^8)

Is this true?
Reply 550
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Gunner121
Can anyone please explain 17 (a) (ii)

http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/January%202009/6PH02_01_que_20090115.pdf
(edited 10 years ago)
Original post by LegendX
I can do the calculation but how do you know what colour they are? :confused:


Simple, rainbows. Red, Orange, Yellow, Green, Blue, Indigo, Violet. Red has the highest wavelength/lowest frequency and Violet has the lowest wavelength/highest frequency.
Reply 552
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Jaydude
11
Original post by Gunner121


Very hard to explain, but:

In standing wave the prticles either oscillate up, down, or do not oscillate at all.

Here We can see series of maximum and minumum amplitudes.

At Y, next to a minumum, it will move up

At Z, it will move down. Look at maximum amplitude next to Z. It cant go any further up, can it? It has to move down. So therefore Z goes down too. Look at X if it helps.

Hope that made sense :smile:
Original post by Water_fall
Can someone please tell me why the answer to question 9 June 2010 is C? Im so confused :frown:


ts refractive index so that = sin i/sin r (its in reference sheet on the exam paper)
Therefore it is sin W/ sin Y your answer sheet is wrong man
(edited 10 years ago)
Reply 554
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Gunner121
Original post by Jaydude
Very hard to explain, but:

In standing wave the prticles either oscillate up, down, or do not oscillate at all.

Here We can see series of maximum and minumum amplitudes.

At Y, next to a minumum, it will move up

At Z, it will move down. Look at maximum amplitude next to Z. It cant go any further up, can it? It has to move down. So therefore Z goes down too. Look at X if it helps.

Hope that made sense :smile:


Thank you so much and can please explain "Q 12 (c)"
http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/January%202009/6PH02_01_que_20090115.pdf
Reply 555
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Jaydude
11
Original post by Gunner121


Opposite to other question. This is a progressive wave now.

So In progressive wave, the only place where particles do not oscillate are at maximum and minimum amplitudes.

The particles act like balls thrown in the air. What happens when a ball reaches its highest point? It stops, i.e particle is at rest at a maximum amplitude. (And min)
Reply 556
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Jaydude
11
Good Luck everyone!
Original post by Jaydude
I read refractive index for light passing through any medium must be greater than 1. (Due to speed of light in vacuum cant exceed 3*10^8)

Is this true?


I don't know about the reasoning you mentioned. But it's true refractive index of any object should be more than 1.
Reply 558
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Gunner121
Original post by Jaydude
Opposite to other question. This is a progressive wave now.

So In progressive wave, the only place where particles do not oscillate are at maximum and minimum amplitudes.

The particles act like balls thrown in the air. What happens when a ball reaches its highest point? It stops, i.e particle is at rest at a maximum amplitude. (And min)

Thanks
Original post by Superhans34
ts refractive index so that = sin i/sin r (its in reference sheet on the exam paper)
Therefore it is sin W/ sin Y your answer sheet is wrong man




Oh sorry I meant June 2010 question 10 :smile: The answer is C but i dont know why :/

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