You are Here: Home >< Physics

# Edexcel Physics Unit 2 "Physics at work" June 2013 Watch

• View Poll Results: The last question - Does resistance increase or decrease?
It increases ( using V=IR or some other method)
70.73%
It decreases using the 'lattice vibrations' theory
29.27%

1. (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
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
2. (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
3. (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

Posted from TSR Mobile
4. (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

Posted from TSR Mobile

I understand that ultraviolet has higher frequency than radio waves but how does this relate to colour?
5. (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.
6. (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?
7. (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!
8. Can someone please tell me why the answer to question 9 June 2010 is C? Im so confused
9. (Original post by LegendX)
I understand that ultraviolet has higher frequency than radio waves but how does this relate to colour?
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.
10. 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?
11. Can anyone please explain 17 (a) (ii)

http://www.edexcel.com/migrationdocu...e_20090115.pdf
12. (Original post by LegendX)
I can do the calculation but how do you know what colour they are?
Simple, rainbows. Red, Orange, Yellow, Green, Blue, Indigo, Violet. Red has the highest wavelength/lowest frequency and Violet has the lowest wavelength/highest frequency.
13. (Original post by Gunner121)
Can anyone please explain 17 (a) (ii)

http://www.edexcel.com/migrationdocu...e_20090115.pdf
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
14. (Original post by Water_fall)
Can someone please tell me why the answer to question 9 June 2010 is C? Im so confused
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
15. (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
Thank you so much and can please explain "Q 12 (c)"
http://www.edexcel.com/migrationdocu...e_20090115.pdf
16. (Original post by Gunner121)
Thank you so much and can please explain "Q 12 (c)"
http://www.edexcel.com/migrationdocu...e_20090115.pdf
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)
17. Good Luck everyone!
18. (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.
19. (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
20. (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 The answer is C but i dont know why :/

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: December 18, 2013
Today on TSR

### Best unis for graduate salaries

Half of the top 10 aren't even RG...

### Should I ask for his number?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

## Make your revision easier

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE