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# Edexcel Physics Unit 2 25th May 2012 Tweet

Physics exam discussion - share revision tips in preparation for GCSE, A Level and other physics exams and discuss how they went afterwards.

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1. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Liver2029)
Yes, but we're talking about polarized light. When light is reflected off a surface it is typically plane polarized to a horizontal plane. The polarizing filter works by absorbing polarized light on the horizontal plane and allowing the passage of polarized light on the vertical plane. Which reduces the light intensity.
not sure im getting you here...when light is reflected no polarisation takes place, reflection and polarization have absolutely nothing to do with eachother. where did you get that from?
and i repeat for the third time that only the light travelling along the same plane of polarization as the poilarizer passes...so if, for example, sunglasses are set to horizontal, but the light is travelling along the vertical plane, then NO light will pass the polarizer
2. (Original post by youlostme)
not sure im getting you here...when light is reflected no polarisation takes place, reflection and polarization have absolutely nothing to do with eachother. where did you get that from?
and i repeat for the third time that only the light travelling along the same plane of polarization as the poilarizer passes...so if, for example, sunglasses are set to horizontal, but the light is travelling along the vertical plane, then NO light will pass the polarizer
I'm with youlostme here except light can be polarised when reflected off of a body of water.
3. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Salmonidae)
I'm with youlostme here except light can be polarised when reflected off of a body of water.
oh yes thats right...i assumed he was talking about hard surfaces
4. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Sagacious)
I'm just a nerd who loves the whole unit, but if I had to pick a favourite... electricity.

How's the revising going?
It's going good so far. Wbuu?
5. Which points are important in experiments?

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6. Re: Edexcel Physics Unit 2 25th May 2012
MerveK,
- Significance of de broglie's electron diffraction exp.
- Young's double slit exp.
- Sugar concentration experiment for polarisation.
- the photoelectric exp.
- snells law refraction exp.
- measuring speed of microwaves/sound, using standing waves.
These are the main experiments to go through. Just have a brief idea about the procedure for each, and any significant conclusions that they provide.
For example, de broglie's electron diffraction experiment showed that
electrons [matter] exhibit wave-like properties (because they diffract), when passed through crystals etc.
Good Luck!! Hope this helped.
7. Re: Edexcel Physics Unit 2 25th May 2012
Could someone please explain Q15 b) (ii) from the june 2010 paper??
Attached Files
8. 6PH02_01_que_20100609.pdf (820.0 KB, 79 views)
9. 6PH02_01_msc_20100716.pdf (222.3 KB, 101 views)
10. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by SKK94)
Could someone please explain Q15 b) (ii) from the june 2010 paper??
OK so you know that Power = I x V. Now in this situation the voltage is not going to change because the computer will use a set voltage, so therefore in order for power to decrease the current must also decrease.

The smaller your current gets, the smaller your internal resistance gets. If the internal resistance decreases then you are losing less energy as heat from the power supply, and so the supply is more efficient.

Therefore it is not just double as long because half the power is being used, but more than double because there is also extra power from less 'lost volts'.
11. (Original post by SKK94)
MerveK,
- Significance of de broglie's electron diffraction exp.
- Young's double slit exp.
- Sugar concentration experiment for polarisation.
- the photoelectric exp.
- snells law refraction exp.
- measuring speed of microwaves/sound, using standing waves.
These are the main experiments to go through. Just have a brief idea about the procedure for each, and any significant conclusions that they provide.
For example, de broglie's electron diffraction experiment showed that
electrons [matter] exhibit wave-like properties (because they diffract), when passed through crystals etc.
Good Luck!! Hope this helped.
Thank you

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12. Re: AS (Edexcel) Physics Unit 2 6PH02 May 2012
(Original post by vicky8761)
completely dont understand EMF
Neither, there was once a question that was like "State the difference between EMF and potential difference"
Is EMF internal potential difference, not sure
13. (Original post by babit)
Neither, there was once a question that was like "State the difference between EMF and potential difference"
Is EMF internal potential difference, not sure
Emf is the total amount of potential difference a power supply can generate if there is no internal resistance. I.e the actual p.d produced by the power supply is always lower than emf
14. When the refractive index is low what happens the direction of ray? Away from the normal or close to the normal?

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15. (Original post by MerveK)
When the refractive index is low what happens the direction of ray? Away from the normal or close to the normal?

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The higher the refractive index the further away from the normal (bigger the angle of refraction)
16. (Original post by Salmonidae)
The higher the refractive index the further away from the normal (bigger the angle of refraction)
Thank you

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17. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by youlostme)
not sure im getting you here...when light is reflected no polarisation takes place, reflection and polarization have absolutely nothing to do with eachother. where did you get that from?
and i repeat for the third time that only the light travelling along the same plane of polarization as the poilarizer passes...so if, for example, sunglasses are set to horizontal, but the light is travelling along the vertical plane, then NO light will pass the polarizer
Ok I see your point now, I had to re-read my book which didn't make it clear. My book quotes that "When light is reflect off a surface such as water, it's polarized to the horizontal plane".
18. Re: Edexcel Physics Unit 2 25th May 2012
Hey I just had a physics lesson and we went back over some refraction. I know that when light is entering say a prism from air, it will refract towards the normal. But say that when it carries on through the prism and then reaches the other side and refracts again, apparently it refracts towards the boundary instead this time. Is this true?
19. (Original post by KamilS)
Hey I just had a physics lesson and we went back over some refraction. I know that when light is entering say a prism from air, it will refract towards the normal. But say that when it carries on through the prism and then reaches the other side and refracts again, apparently it refracts towards the boundary instead this time. Is this true?
Yes it will exit the prism parallel to the ray of incidence
20. Re: Edexcel Physics Unit 2 25th May 2012
guys you know for the critical angle formmula sinc=1/n.

sometimes you have to flip it around and sinc = n

in which context do we use either equation??

21. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Megaman1995)
guys you know for the critical angle formmula sinc=1/n.

sometimes you have to flip it around and sinc = n

in which context do we use either equation??

Same problem I have!
22. Re: Edexcel Physics Unit 2 25th May 2012
Does anyone know the equation for the path difference for destructive interference? My teacher told me it's (2n+1)Y/2 the book gives two forms (n+1/2)Y/1/2 and (n+Y)1/2.
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