OCR Physics A G482, Electrons, Waves and Photons, 25th May 2012

Can anyone outline the experiments we'll be expected to know/describe/draw?
Because I know them roughly but when I'm doing practice papers I'm struggling to get full marks because I don't know exactly what OCR want us to put.

Reply 87

Original post by sweetascandy

Terminal p.d. is the potential difference across the external resistor connected to an EMF source. This is the definition which I've learnt :smile:

So what happens if there is multiple resistors all with different resistance? Is the terminal pd the individual pds of each resistor or the summed pds of each resistor?

Reply 88

welshy93

Original post by A for Andromeda

Oops, kind of a fundemental thing to know :colondollar:

Thanks

did the mark scheme just have uv or could you say blue? :confused:

Reply 89

Original post by zonka

can someone list the formulas that we must remember which are not going to be on the formula sheet!! :smile:

intensity = amplitude^2
intensity = power/ cross sectional area
frequency = 1/time period
EMF= IR + Ir
EMF= I(R + r)
EMF= V + v
Malus Law: A= A0 cos theta & I= I0 cos^2 theta

think that is it :smile:

Reply 90

Original post by the real viper

So what happens if there is multiple resistors all with different resistance? Is the terminal pd the individual pds of each resistor or the summed pds of each resistor?

Urmm I'm not really sure; on the spec it says to just know the equation :s-smilie:

but I'm guessing it would mean the sum of the pd's!

Reply 91

Original post by Toshiya

Can anyone outline the experiments we'll be expected to know/describe/draw?
Because I know them roughly but when I'm doing practice papers I'm struggling to get full marks because I don't know exactly what OCR want us to put.

Describe an experiment to obtain the I-V characteristics of a resistor at constant temperature, filament lamp and light emitting diode.

Describe Experiments that demonstrate two-source interference using sound, light and microwaves.

Describe Young double slit experiment.

Describe experiment to determine wavelenght of monochromatic light.

Describe and experiment using LEDs to estimate plancks constant - (The photoelectric effect basically!)

ENJOY! :smile:

Reply 92

Original post by sweetascandy

Urmm I'm not really sure; on the spec it says to just know the equation :s-smilie:

but I'm guessing it would mean the sum of the pd's!

Wait i've just read that the you sometimes take the terminal pd to be the EMF of the supply because you are ignoring internal resistance so therefore the terminal pd must be the sum of the individual pd's i guess!!! :biggrin:

Reply 93

WillKail

Grade boundaries are so low on this paper, have found some of the more recent ones just stupid though, overly vague and focusing on areas that aren't really covered in the book or anything.

Reply 94

Original post by WillKail

Grade boundaries are so low on this paper, have found some of the more recent ones just stupid though, overly vague and focusing on areas that aren't really covered in the book or anything.

agreed, as long as you are getting all the calculations correct and then getting like 2/3 of the explanation questions (sometimes less) you've basically got an A

Reply 95

A for Andromeda

8

Original post by welshy93

did the mark scheme just have uv or could you say blue? :confused:

Only blue/violet - but I'm fairly sure it meantioned something about it being visible (light) in the stem of the question :smile:

Reply 96

Original post by OllyHV

Energy levels. Can somebody try to explain them to me, no matter how many times I read about them in the textbook, I simply can't get my head around them. I would really appreciate it cheers !

- Each element has a unique spectra (of wavelengths).
- Isolated atoms are gas atoms that exert negligible forces on each other. So they absorb/emit light photons of different frequencies, (which is evident from their absorption and emission spectra).
- If you heat a gas, many electrons move to higher energy levels (since they gain more heat energy).
- Absorption line spectra arise when EM radiation is absorbed by isolated atoms. An electron absorbs a photon of the correct energy to allow it to make a transition to a higher energy level. When an electron moves down an energy level, it emits a photon.
- At cool temperatures, electrons are most likely to be at the ground state.

Feel free to correct me where I'm wrong; I don't feel that confident on this topic myself tbh! But I hope it does help someone :smile:

Reply 97

welshy93

Original post by A for Andromeda

Only blue/violet - but I'm fairly sure it meantioned something about it being visible (light) in the stem of the question :smile:

ohh ok thankss :smile:

Reply 98

firstevermember

just done jan 2011 paper, wish i had that paper for real exam was really nice and easy, Mind you i am resitting this unit.

Reply 99