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. guys what is a critical angle ? :O
2. (Original post by x0x)
I said that I decreases
so for a given voltage the resistance should increase
since V=IR
but its true ... when current decreases there is less heating but I depended on the equation since there were 4 marks and in mark schemes they almost always require you to quote a relevant equation :P
Considering it was a 4 mark question, I think a very long explanation should be given e.g. 671 post
3. Estimated grade boundary for an A?

Thanks.
4. (Original post by Freddy-Francis)
guys what is a critical angle ? :O
Angle of incidence at which angle of refraction=90*, so light travels along medium boundary.
5. what did u guys put for the "Explain why the following observations may be understood by using a photon model of light, rather than a wave model"?
6. What did everyone say for the q on stating EM radiation for the since plate photoelectric effect q?

I put UV for two reasons. If you know from experience UV radiation and visible light appear to be associated most with zinc. Also there was a q on radio waves frequency from before like the start of the paper, which was a small hint, from that I realised that this unknown radiation is above both visible light and radio waves in terms of frequency, so it's either UV, X-ray, gamma. Due to first reason I put down UV, I have more faith in it.
7. (Original post by krisshP)
Estimated grade boundary for an A?

Thanks.
im thinking 58-59
8. (Original post by krisshP)
What did everyone say for the q on stating EM radiation for the since plate photoelectric effect q?

I put UV for two reasons. If you know from experience UV radiation and visible light appear to be associated most with zinc. Also there was a q on radio waves frequency from before like the start of the paper, which was a small hint, from that I realised that this unknown radiation is above both visible light and radio waves in terms of frequency, so it's either UV, X-ray, gamma. Due to first reason I put down UV, I have more faith in it.
its UV since frequency was 1.04x10^15 or something and i memorized the wavelengths and this one ws 2.somethingx10^-7 which is UV
9. (Original post by Freddy-Francis)
what did u guys put for the "Explain why the following observations may be understood by using a photon model of light, rather than a wave model"?
It was a QWC question worth 5 marks I thin. I ended up just stating stuff like
One photon releases one electron
E=hf
Wave energy depends on frequency for particle model an on intensity for wave model
Energy supply is continuous, so can build up for wave model
....
10. (Original post by hamzeh h)
its UV since frequency was 1.04x10^15 or something and i memorized the wavelengths and this one ws 2.somethingx10^-7 which is UV
It just said which part.
So i put the high end
And put examples like xrays, gamma rays :O
11. (Original post by Freddy-Francis)
what did u guys put for the "Explain why the following observations may be understood by using a photon model of light, rather than a wave model"?
its repeated in many pastpapers just expain about one photon giving energy to one electron and frequency being propoptional to energy..etc and that if it was a wave keeping the light shone will accumulate energy and electrons will be emitted but doesnt happen and talk about threshold frequency
12. (Original post by Freddy-Francis)
It just said which part.
So i put the high end
And put examples like xrays, gamma rays :O
well Ultra-violet is a part of electromagnetic spectrum :P
13. (Original post by krisshP)
It was a QWC question worth 5 marks I thin. I ended up just stating stuff like
One photon releases one electron
E=hf
Wave energy depends on frequency for particle model an on intensity for wave model
Energy supply is continuous, so can build up for wave model
....
i put the similar as u.
I also put that the number of photoelectrons emitted per second is proportional to the intensity of radiation. <<any marks/
14. (Original post by hamzeh h)
its UV since frequency was 1.04x10^15 or something and i memorized the wavelengths and this one ws 2.somethingx10^-7 which is UV
The radio waves v=flambda question on section b was a nice hint helping for this question, I'm surprised nobody made use of it.
15. (Original post by krisshP)
The radio waves v=flambda question on section b was a nice hint helping for this question, I'm surprised nobody made use of it.
yaa
16. (Original post by hamzeh h)
yaa
Did you do that as well? Look at post 685, that's how I figure it out. They expected you to be so cunning.
17. qu6) the transition which did u guys choose? 5 to 4?
18. (Original post by Freddy-Francis)
qu6) the transition which did u guys choose? 5 to 4?
4 to 5 it was absorption of lowest frequency
19. Grade boundries estimates for the A guys?
20. (Original post by Freddy-Francis)
qu6) the transition which did u guys choose? 5 to 4?
I did 4 to 5 beacuse it was being absorbed

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

### Last-minute PS help

100s of personal statements examples here

### More pressure for kinky sex?

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

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

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.