AQA Physics A - PHYA5 (18/06/12) - Exam thread

Guys is output power of a star proportional to its distance square from earth??

I should get minimum A, most likely A* though, which would be nice, i got 113 in Unit 4 so that would seal an A* but it wouldnt be the end of the world

i got 113 in Unit 4

No problem. We know that 30000J are given out by the lead as it changes state, and we know that 75240 is absorbed in total!

To work out the amount of energy given out by the lead due to heat change, we take the TOTAL energy given out, and subtract the STATE CHANGE energy.

75240 - 30000 = 45240.

This energy is the amount given out due to the change in temperature, and so we can use the formula:

Q = mc delta T

Subbing in values:

45240 = 1.2 x (327-84) x c
c = 155

Did this help at all?

LB

How the f***?!?

Nobody knows

I don't think they've ever repeated a 6 marker. So it could be on absolutly anything and likely something we've never seen before. Though for some reason I have a hunch it will be to do with nuclear stuff.

Would anyone be able to tell me how many marks/ums I need on this paper to get a B overall for my A Level?
My marks so far are ;
U1 98
U2 102
U3 45ish
U4 84 (if I discard the resit I did)
U6 44ish
All in ums




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What value of ro are we supposed to use for nuclear radius? The textbook says 1.05fm, but my revision guide says 1.4fm.

What value of ro are we supposed to use for nuclear radius? The textbook says 1.05fm, but my revision guide says 1.4fm.

You're going for an A/B at A level physics and you cant take some numbers away from 420? I dont mean to be rude but come on

I always wonder that too when I see these posts, especially in maths exam threads

Here's a couple of possible 6 markers for Astro!

Explain how a CCD is used to produce an image:

- A CCD is a silicon chip divided into pixel.
- Incident photons cause electrons to be released.
- Number of released electrons is proportional to the intensity of the light source.
- Electron pattern build up which is identical to the image formed on the CCD.
- When fully exposed, charge is processed to produce image.
- Quantum efficiency of a CCD is greater than 70%.
- Nearly 20x more efficient than photographic film.

Explain the formation of a star:

- Gas & dust clouds compress due to their gravitational attraction (protostar is formed).
- Graviational potential energy converted to thermal energy as the atoms gain kinetic energy and collide more frequently.
- Core becomes hot enough for nuclear fusion to occur.
- As more & more matter is pulled in and compressed, nuclear fusion continues.
- Outer layers around the core heat up and a photosphere is formed.
- The protostar is now a star.

Explain Hydrogen Balmer absorption lines:

- Atmosphere of the star has hydrogen atoms with electrons in the n=2 stae.
- Light from the star passes through the atmosphere of the star.
- Electrons are excited into higher energy states.
- They can only absorb certain amounts of energy.
- These certain energies are related to specific frequencies.
- The electrons de-excite, through different energy level changes.
- When the electrons de-excite, the light is radiated in all directions.
- The intensity of the light at particular frequencies is reduced, resulting in absorption lines.

Explain how Type 1A supernovae occur and how they can be used to find the distance from Earth:

- White dwarf increases in mass as it attracts material from its companion in the binary system.
- It reaches its critical mass such that fusion can resume.
- The released of energy cayses the star to explode in a supernova.
- Rapid & enormous increase in absolute magnitude.
- Always reaches peak of -19.3 so it can be used as a standard candle to find the distance of the galaxy.

what is a quasar?

is it a black hole or is it produced by a black hole?