Edexcel Physics Unit 2 &quot;Physics at work&quot; June 2013

guys what is a critical angle ? :O

Reply 681

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

Reply 682

Estimated grade boundary for an A?

Thanks.

Reply 683

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.

Reply 684

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"?

Reply 685

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.

Reply 686

Original post by krisshP

Estimated grade boundary for an A?

Thanks.

im thinking 58-59

Reply 687

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

Reply 688

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
....

Reply 689

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 didnt ask for specific..
It just said which part.
So i put the high end :eek:

And put examples like xrays, gamma rays :O

Reply 690

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

Reply 691

Original post by Freddy-Francis

it didnt ask for specific..
It just said which part.
So i put the high end :eek:

And put examples like xrays, gamma rays :O

well Ultra-violet is a part of electromagnetic spectrum :P

Reply 692