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

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Original post by Dale12
is it just me or does anyone else get confused on the power section about calculating e.m.f and determining p.d through resistors in parallel etc :colondollar: ?


yeah for me personally its my weakest area :/
Reply 201
Original post by goerigi

Original post by goerigi
yeah for me personally its my weakest area :/


same andi keep doing question after question but still not sinking in abhout how to go about doing them :/ just gotta hope they dont come up tomorrow much :/
Reply 202


Thanks, much appreciated :biggrin:
Reply 203
Hi guys, anyone know why the photoelectric current in a photocell circuit is proportional to intensity of the incident radiation?

Cheers :smile:
Reply 204
guys is this a am or pm exam ????????
Reply 205
Original post by jake9382

Original post by jake9382
guys is this a am or pm exam ????????


pm
Reply 206
Original post by jake9382
guys is this a am or pm exam ????????


Afternoon.
Reply 207
Original post by Zobinho

Original post by Zobinho
Hi guys, anyone know why the photoelectric current in a photocell circuit is proportional to intensity of the incident radiation?

Cheers :smile:


what section of the specification is that in???
Reply 208
Original post by Dale12
what section of the specification is that in???


2.5.2 The Photoelectric effect
http://www.ocr.org.uk/download/kd/ocr_9587_kd_gce_spec.pdf
scroll down page 27
Original post by Zobinho
Hi guys, anyone know why the photoelectric current in a photocell circuit is proportional to intensity of the incident radiation?

Cheers :smile:


I don't think we have to know that for this exam; it's not on the spec.

EDIT: Okay, maybe it is :colondollar:
(edited 12 years ago)
Reply 210
Original post by Zobinho
Hi guys, anyone know why the photoelectric current in a photocell circuit is proportional to intensity of the incident radiation?

Cheers :smile:


Here's something about this from earlier today.
Reply 211
Original post by Zobinho

Original post by Zobinho
2.5.2 The Photoelectric effect
http://www.ocr.org.uk/download/kd/ocr_9587_kd_gce_spec.pdf
scroll down page 27


ah, imagine a photocell as a cell that needs em radiation to shine on it to release electrons.. E=hf...
the maximum kinectic energy of the electrons is independent of intensity because only 1 photon will interact with 1 electron... however, increasing intensity increases the number of photons that hit the photocell per second... if more photons are interacting with more electrons per second, then more electrons will be released per second and allowed to flow around the circuit... more charge carriers per second results in an increase in current... hope that helps
Original post by Dale12
ah, imagine a photocell as a cell that needs em radiation to shine on it to release electrons.. E=hf...
the maximum kinectic energy of the electrons is independent of intensity because only 1 photon will interact with 1 electron... however, increasing intensity increases the number of photons that hit the photocell per second... if more photons are interacting with more electrons per second, then more electrons will be released per second and allowed to flow around the circuit... more charge carriers per second results in an increase in current... hope that helps


Omg, that makes SO much sense! I would +rep you but "You have reached the limit of how many posts you can rate today!" :colondollar:
Reply 213
Original post by sweetascandy

Original post by sweetascandy
Omg, that makes SO much sense! I would +rep you but "You have reached the limit of how many posts you can rate today!" :colondollar:


im just glad it helped you :smile: in fairness i completely forgot about that, had to qucikly read through my notes from a couple days ago :biggrin:
Reply 214
Quick question; something which the (useless) textbook hasn't helped me with.

With Waves, what is the difference between Amplitude and Displacement? Are they basically the same numerical value, except Amplitude is always positive whilst Displacement can be positive or negative, depending on whether it is above or below the line?

Cheers :smile:
Original post by JoshC.
Quick question; something which the (useless) textbook hasn't helped me with.

With Waves, what is the difference between Amplitude and Displacement? Are they basically the same numerical value, except Amplitude is always positive whilst Displacement can be positive or negative, depending on whether it is above or below the line?

Cheers :smile:


Amplitude = the maximum displacement from the equilibrium position.
Displacement = the displace of any point on a wave from its equilibrium position.

So amplitude is the peak, whereas displacement is just simply the distance of any point of the wave (e.g. it could be halfway between equilibrium position and amplitude) from its equilibrium position.

Hope that helps :smile:
(edited 12 years ago)
Reply 216
Original post by JoshC.

Original post by JoshC.
Quick question; something which the (useless) textbook hasn't helped me with.

With Waves, what is the difference between Amplitude and Displacement? Are they basically the same numerical value, except Amplitude is always positive whilst Displacement can be positive or negative, depending on whether it is above or below the line?

Cheers :smile:


my textbook says AMPLITUDE = the maximum displacement of a particle from its equilibrium position... so for instance, if you think of a sin wave.. then its amplitude is at 90 degrees whilst at say 45 degrees its displacement would be 0.707... if that makes sense?
Reply 217
Original post by Dale12
my textbook says AMPLITUDE = the maximum displacement of a particle from its equilibrium position... so for instance, if you think of a sin wave.. then its amplitude is at 90 degrees whilst at say 45 degrees its displacement would be 0.707... if that makes sense?


Thanks to you both, but that Maths-y way of describing it really has helped.

Cheers! :biggrin:
Reply 218
Can someone explain to me the relationships between current, voltage, and resistance.

eg.

- If you change the voltage supplied, how does the resistance and current change?
- If you increase the resistance, does the current decrease but the voltage stay the same?

Struggling to get my head round all this!
Original post by Wilko94
Can someone explain to me the relationships between current, voltage, and resistance.

eg.

- If you change the voltage supplied, how does the resistance and current change?
- If you increase the resistance, does the current decrease but the voltage stay the same?

Struggling to get my head round all this!


I just learnt this today.
Think of voltage as something which helps to push the current round a circuit.
When there's a high resistance and low current, then the voltage needs to increase so that it can push the current around faster.
On the other hand, when there's a low resistance but high current, the voltage doesn't need to push the current round since it's already high; hence the voltage decreases.

Btw, I don't think this is the actual scientific way of explaining it; it's just to help you understand it. :smile:

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