Edexcel Physics IGCSE 1P Unofficial Mark Scheme 25th May 2016

The hairs weren't dense enough to slow down the uv enough for total internal reflection to occur

(I think)

I asked my tuition teacher he said that TIR does happen on the edges of the hollow tube….there is a small gap between the edge and the hair so TIR takes place there…..however the question ask why it doesnt reach the skin so the answer is absorption…..furthermore to prove this remember they asked us about the image of the UV…..the polar bear was black suggesting it doesnt radiate UV but it is absorbed by the hair…… so its absorption…..plus its 2 marks nothing much to worry about…

Reply 101

Bede735

1

Original post by pro567

I asked my tuition teacher he said that TIR does happen on the edges of the hollow tube….there is a small gap between the edge and the hair so TIR takes place there…..however the question ask why it doesnt reach the skin so the answer is absorption…..furthermore to prove this remember they asked us about the image of the UV…..the polar bear was black suggesting it doesnt radiate UV but it is absorbed by the hair…… so its absorption…..plus its 2 marks nothing much to worry about…

Well your tutor is defying the laws of physics, TIR cannot take place from a low refractive to high refractive index medium, not unless n < 0, which it is safe to say polar bear fur isn't. That was an IR camera, not UV. No creatures skin radiates substantially in UV, to do so it would have to be too hot.

Reply 102

da lesh

Hey I need help please, For the question about motors, the split ring commutators and the brushes, I just put that they prevent the wire from tangling up and switch the direction of the current every half turn so the motor spins in one direction. Did I have to put exactly what the commutator and the brushes did independently or would what I wrote be correct? Thanks.

Reply 103

da lesh

Hey I need help please, For the question about motors, the split ring commutators and the brushes, I just put that they prevent the wire from tangling up and switch the direction of the current every half turn so the motor spins in one direction. Did I have to put exactly what the commutator and the brushes did independently or would what I wrote be correct? Thanks.

Original post by Bede735

Well your tutor is defying the laws of physics, TIR cannot take place from a low refractive to high refractive index medium, not unless n < 0, which it is safe to say polar bear fur isn't. That was an IR camera, not UV. No creatures skin radiates substantially in UV, to do so it would have to be too hot.

Reply 104

kayamh

7

Original post by conradliebers

Thanks a lot! It was stage 9.

Sorry, could you explain why?

Reply 105

Bede735

1

Original post by da lesh

Hey I need help please, For the question about motors, the split ring commutators and the brushes, I just put that they prevent the wire from tangling up and switch the direction of the current every half turn so the motor spins in one direction. Did I have to put exactly what the commutator and the brushes did independently or would what I wrote be correct? Thanks.

I wouldn't dwell too much on the exam and concentrate on revision for paper 2. However, what you wrote is correct (although the order in which you wrote them would need to be the other way round if they are in the same direction as their use). I haven't seen a mark scheme so I suppose it would depend on how many marks were available for the question.

Reply 106

conradliebers

OP

11

Original post by amkay

Sorry, could you explain why?

You literally just got your ruler out, and at stage 9, the planet and comet were closest to each other.

Reply 107

VaJJGear

It really was a hard exam. Physics was one of the subjects that I could have achieved an A* in, now we're hoping for an A!

Reply 108

Hsevras

2

Original post by VaJJGear

It really was a hard exam. Physics was one of the subjects that I could have achieved an A* in, now we're hoping for an A!

grade boundaries will be low though

Reply 109

TudorAddict

3

I think it was a challenge and the questions were a bit unusual but after looking at this, I think I did better than I thought I did. Coming out of the exam though, I thought it was very brutal.

Reply 110

cookie123456789

4

It was possibly the hardest exam I've ever done!

Mark scheme for 1PR?

IF u GUYZ WANT 1P paper . i have a soft copy of it on my PC.. dont ask me how i got it.. just i have it...TSR plz tell me it isnt illegal to share... if it is then i wont share ....