# Lets revise physicsA2 togather ultimate thread

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15 years ago
#81
I hate the photoelectric effect so much! Makes no sesne!

Err voltage to stop photoelectrons being emitted? I really have no idea lol
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15 years ago
#82
(Original post by mc_watson87)
I hate the photoelectric effect so much! Makes no sesne!

Err voltage to stop photoelectrons being emitted? I really have no idea lol
ok so lets try to learn this stuff. Any one got any gd explanations for this stuff?
i set the topic, but that dont mean i kno the stuff
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15 years ago
#83
for me its more like a ......
Lets learn physicsA2 togather ultimate thread
rather than
Lets revise physicsA2 togather ultimate thread
and the exams are gettn soo close
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15 years ago
#84
what module/board is the photoelectric effect photocurrent etc or whatever you are talking about, it seems alien to me!
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15 years ago
#85
its edexcel module 4
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15 years ago
#86
i learnt the effect thru the grafs u get....try that its more visual...supplement it with sum notes on the grafs at what happens at the points on the graf
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15 years ago
#87
Im going over the photoelectric effect.

A question in the June 2003 was really tough. It had a graph of T/KE(J) against Freq, and for 3 marks it asked you to find H from the graph.

So how do you rearrange hf=[phi]+T, to make a straight line(corresponding to y=mx+c) with T the subject?
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15 years ago
#88
(Original post by SinghFello)
Im going over the photoelectric effect.

A question in the June 2003 was really tough. It had a graph of T/KE(J) against Freq, and for 3 marks it asked you to find H from the graph.

So how do you rearrange hf=[phi]+T, to make a straight line(corresponding to y=mx+c) with T the subject?
Um t= hf - [phi] ?

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15 years ago
#89
lol, im so stupid..
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15 years ago
#90
(Original post by BCHL85)
1) An alpha particle of mass 4u is emitted from a nucleus of mass 226u. If energy E is released as kinetic energy, find the kinetic energy of each particle in terms of E.
Such a weird one.
K.E of alpha particle = E.
The nuclei before and after radiation will not moving. So their K.E = 0. But I'm not so sure it's right or not.
That's wrong, it's a collision and the impulse on the nucleus will be the same as that on the alpha particle so it will move. Just like if you put an explosive between a small and large ball, the small one will be shot out much faster. As kinetic energy is proportional to v^2 and only m^1, the alpha particle will have muc more energy, you just need to work out the ratio.
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#91
(Original post by mc_watson87)
I hate the photoelectric effect so much! Makes no sesne!

Err voltage to stop photoelectrons being emitted? I really have no idea lol
yeah
as you see electrons are negative so as you increase v(the potential differnece)you make the recieving electrode more negative so it repels the electrons
at a pont where no more electrons can reach the recieving electrode;it's like you convert all of the kinetic energy of the elctrons into potential energy to travel through the potential differenece,moreover the electrical potential energy is QV,and the pd where all KE was converted to PE is the stopping voltage so PE=QV(s)
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#92
(Original post by sumitk87)
Come on people lets continue with this now, practicals are over lets revise for phy4 phy5 phy6. I kno i just repeated what habosh said but im trying to bump the thread .

To re-start the revision.....

How would you define stopping voltage (photocurrent stuff)
it's the voltage at which no more electrons of even the fastest electrons are stopped from reaching the recieving electrode
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15 years ago
#93
can i ask why longitudinal waves can't be polarised?
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#94
(Original post by lilbug)
can i ask why longitudinal waves can't be polarised?
polarsation confines the waves to one direction of travel as they oscillate perpindicular to their direction of travel while long itudinal travel parallel to the direction of travel so they can't be polarised
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15 years ago
#95
i knew those definitions but i thought there was a more detailed explanation, well i thought about it more. you're right and i feel silly. doh!
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15 years ago
#96
wat does it mean by de broglie wavelength?
is it that a particle travels the same shape as a wave (sinusodially) or the particle has a wavelength? bit confused as i aint revised unit 4 for a very long time
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15 years ago
#97
(Original post by bassman)
bit confused as i aint revised unit 4 for a very long time
same... wish i hadn't buggered it in january can't do the ole wave-particle duality nonsense

still its all better than PHY6
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15 years ago
#98
(Original post by bassman)
wat does it mean by de broglie wavelength?
Simply, the wavelength is Plack divided by the momemtum. so any moving mass has a wavelength.

Wavicle Duality:

Waves as particles:
Specific photon energies/quantised using E=hf in the photoelectric effect
(Wave proof = when going through a single slit)

Particles as Waves:
De Broglie eqn - if velocity is constant wavelength is invs proportional to mass
Electron diffraction
(Particle proof = actual mass)
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15 years ago
#99
(Original post by corkskrew)
Simply, the wavelength is Plack divided by the momemtum. so any moving mass has a wavelength.

Wavicle Duality:

Waves as particles:
Specific photon energies/quantised using E=hf in the photoelectric effect
(Wave proof = when going through a single slit)

Particles as Waves:
De Broglie eqn - if velocity is constant wavelength is invs proportional to mass
Electron diffraction
(Particle proof = actual mass)
thanks, but what does it mean by 'any moving mass has a wavelength'?

sorry for askin stupid questions lol
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#100
(Original post by bassman)
thanks, but what does it mean by 'any moving mass has a wavelength'?

sorry for askin stupid questions lol
it's like you have a wavelength,I have a wavelength the bug flying around you annoying you all the time has a wavelength,but it's just the wavelength is too small so it effect cannot be noticed
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