# OCR Physics Unit 2 - G482 - (June Exams Preparation) Watch

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#461

Has someone here posted the answers to the possible experiment questions that can come up? If so can someone refer me to it and if not can someone post them? Even one may help, I don't know any of them and this will help a great deal!!

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#462

Do we have to know the speed of sound in a resonance tube experiment (or checking nodes and antinodes of a microwave with a probe)?

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#463

(Original post by

If you think about the equation for a straight line: y= mx + c

and put the quantities in, you get: KEmax = mf + c

Then think about the equations you know involving KEmax and f (which is one according to the formula booklet I think!) this equation is hf = work function + KEmax

Rearrange: KEmax = hf - work function

also KEmax = mf + c as already found.

So h=m so h is the gradient

and c = -work function so -work function is the y intercept.

Also worth knowing that the x intercept is the threshold frequency

**_hail**)If you think about the equation for a straight line: y= mx + c

and put the quantities in, you get: KEmax = mf + c

Then think about the equations you know involving KEmax and f (which is one according to the formula booklet I think!) this equation is hf = work function + KEmax

Rearrange: KEmax = hf - work function

also KEmax = mf + c as already found.

So h=m so h is the gradient

and c = -work function so -work function is the y intercept.

Also worth knowing that the x intercept is the threshold frequency

Yeah I thought it'd be the gradient = h, but even then the values still don't plug in correctly.

For example, when answering I used 40x10^-20 on the y axis, with 15x10^14 on the x, but according to the markscheme it should have been 6.25x10^14 instead of my value of x

I'm probably missing something stupid, but I still just don't get it

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#464

**Standing wave experiments both wave types (longitudinal+transverse) can produce standing waves.**to set up a standing wave you can use a microwave and a metal sheet,

1) place the metal sheet some distance away from the microwave, exactly n or n.5 wavelengths away from the generator

2) microwaves will travel to the metal sheet and be reflected back upon themselves and travel in the opposite direction where they will superpose/interfere to create points of displacement equal to the amplitude [antinodes], and no displacement [nodes]. In this wave type energy is trapped in pockets and no energy is transferred, unlike a normal progressive wave.

3) measure the points of node and antinode using a microwave detector and moving it along the wave, you should detect points of zero amplitude meaning you have found a node, if you continue along it you should find a point of maximum displacement (a.k.a. amplitude), the distance between these points is (wavelength/4) from which you can determine the wavelength of the microwave.

__Measuring the speed of sound using an air column.__firstly you will need a tuning fork of known frequency, then you need to determine the wavelength, before using v=fx(wavelength), to determine the wavelength you can set up a standing wave in a air colum, this consists of a column of water where you should clang the fork until you hear it resonate and add the water until you reach the fundemental frequency which is where the water cannot be any higher to produce a resonant sound, from this you can determine the wavelength as the length of the tube at this frequency is ¼(wavelength) but you need to add a constant called end correction because the node forms slightly above the water!

__Youngs Double Slit__1) COHERENT light from the same source (constant phase difference)

2) 2 parallel narrow slits in an obstacle, a screen behind them

3) Light from the source passes through both slits and is diffracted

4) Interference occurs between the light from each slit at the screen

5) if waves arrive with a path difference of a multiple of whole wavelengths (n*lamda), cons interference - maxima , Arrive with a path difference of an odd multiple of half wavelengths ((n+1)/2 * lamda), destructive interference= minima

__Describe an experiment to measure and obtain the Planck Constant, mentioning apparatus used and methods implemented__

When an LED emits light, each electron that passes through it loses a fixed amount of energy: this energy corresponds to the energy of the emitted light. Therefore the energy lost by the electron = charge on electron x potential difference across LED. So hf=eV . The frequency of the LED light is known (manufacturers label). Setting up a circuit using an LED; a variable p.d supply is connected to the LED and increased from 0 until the LED begins to glow. The potential difference is measured for several different coloured LEDs. A graph of eV against frequency f is then plotted and the gradient of the graph is h.

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#465

(Original post by

Yeah I thought it'd be the gradient = h, but even then the values still don't plug in correctly.

For example, when answering I used 40x10^-20 on the y axis, with 15x10^14 on the x, but according to the markscheme it should have been 6.25x10^14 instead of my value of x

I'm probably missing something stupid, but I still just don't get it

**xomaxhox**)Yeah I thought it'd be the gradient = h, but even then the values still don't plug in correctly.

For example, when answering I used 40x10^-20 on the y axis, with 15x10^14 on the x, but according to the markscheme it should have been 6.25x10^14 instead of my value of x

I'm probably missing something stupid, but I still just don't get it

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#466

Do you lose marks if you add extra information? For example if it says define potential difference and you wrote ' energy transfer per unit charge from electrical to other forms' and also wrote 'measured in volts' would you lose a mark for putting measured in volts?

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#467

(Original post by

Do you lose marks if you add extra information? For example if it says define potential difference and you wrote ' energy transfer per unit charge from electrical to other forms' and also wrote 'measured in volts' would you lose a mark for putting measured in volts?

**Lucas96**)Do you lose marks if you add extra information? For example if it says define potential difference and you wrote ' energy transfer per unit charge from electrical to other forms' and also wrote 'measured in volts' would you lose a mark for putting measured in volts?

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#468

Its not likely that the led experiment for plancs constant will come up is it? Since it came up in jan 2013

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#469

(Original post by

Yeah hahaha what you're doing is reading off the value of x instead of the change in x, I think it would be (15-9 or whatever it is) x 10^14 Hz

**_hail**)Yeah hahaha what you're doing is reading off the value of x instead of the change in x, I think it would be (15-9 or whatever it is) x 10^14 Hz

Oh wow, I knew it would be something like that haha

Appreciate the help - it's been a long exam period!

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#471

**Lucas96**)

Do you lose marks if you add extra information? For example if it says define potential difference and you wrote ' energy transfer per unit charge from electrical to other forms' and also wrote 'measured in volts' would you lose a mark for putting measured in volts?

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#472

(Original post by

Oh wow, I knew it would be something like that haha

Appreciate the help - it's been a long exam period!

**xomaxhox**)Oh wow, I knew it would be something like that haha

Appreciate the help - it's been a long exam period!

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#473

im extremely stuck on quantum

can somene pls pls help!!!

can somebody tell me about emission spectrum, line spectrum, define spectral line, define emission and line spectrun, define band spectrum, tell me why emission and absorption spectrum are used,

describe what an absorption spectra and emission line spectra look like

what gas u need for them

i really flopped my chemistry n other exams, n neeeeeeed a really good mark in physics, n really wud appreciate help!!!

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can somene pls pls help!!!

can somebody tell me about emission spectrum, line spectrum, define spectral line, define emission and line spectrun, define band spectrum, tell me why emission and absorption spectrum are used,

describe what an absorption spectra and emission line spectra look like

what gas u need for them

i really flopped my chemistry n other exams, n neeeeeeed a really good mark in physics, n really wud appreciate help!!!

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#474

Panicking so much about my lack of knowledge for this paper, especially the quantum areas.

Someone please help me, I'm so stressed out

Someone please help me, I'm so stressed out

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#475

I think like 90% of people are going into this exam not 100% prepared. Don't worry , grade boundaries WILL be low :P

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#476

(Original post by

I think like 90% of people are going into this exam not 100% prepared. Don't worry , grade boundaries WILL be low :P

**scientific222**)I think like 90% of people are going into this exam not 100% prepared. Don't worry , grade boundaries WILL be low :P

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#477

(Original post by

LOOL i've always hated waves, its just bull.

**Dizzie31**)LOOL i've always hated waves, its just bull.

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#478

(Original post by

Its my weak area too, I can pretty much get 70-80% of the marks in electricity as a minimum. My waves is horrific. At this stage if you still don't understand the concepts I would recommend memorising the mark scheme/experiments. A lot of the marks can be picked up by simple calculations and definitions/experiments. Leaving out the "new" unknown questions would still get you an A, because you are allowed to lose around 30 marks on minimum for an A

**scientific222**)Its my weak area too, I can pretty much get 70-80% of the marks in electricity as a minimum. My waves is horrific. At this stage if you still don't understand the concepts I would recommend memorising the mark scheme/experiments. A lot of the marks can be picked up by simple calculations and definitions/experiments. Leaving out the "new" unknown questions would still get you an A, because you are allowed to lose around 30 marks on minimum for an A

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#479

I still haven't learnt ANY definitions. I'm gonna go into school 2 hours before the exam tomorrow and learn as much as possible.

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#480

(Original post by

What do we need to know off by heart that isn't in the formula book?

**speedstar_mm**)What do we need to know off by heart that isn't in the formula book?

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