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HSC Physics Marathon 2013-2015 Archive (3 Viewers)

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Mr_Kap

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re: HSC Physics Marathon Archive

Relativity of simulteneity: 2 events that are simultaneous in one frame of reference will NOT be simultaneous in any other inertial frame of reference.

2011 HSC Q24 is a question on this.

My answer to that is:

The method would work only from the perspective of an observer relative to the inertial reference frame of the ship. An observer on Earth would see the light from the bulb reach clock A first as this clock will approach the light. This is because the observer on Earth would measure the speed of light to be a constant value in all directions. The light would hit B later because it is receding from the light bulb. This is a consequence of the theory of special relativity in which we can no longer regard time as an absolute quantity. This means that whether two events are determined to be simultaneous depends on the motion of an observer. This is called the relativity of simultaneity.
 
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Drsoccerball

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re: HSC Physics Marathon Archive

With your knowledge on astrophysics describe a way to find a black hole.
 

Crisium

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atargainz

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re: HSC Physics Marathon Archive

Explain the operation of solar cells with the aid of a diagram. [6 marks]
 

TQuadded

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re: HSC Physics Marathon Archive

I'm contemplating a lot about Einstein's theory. He's a smart guy to propose something that is barely possible to test, like the mirror on a train travelling at the speed of light one. I don't believe a word he said.
 
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I'm contemplating a lot about Einstein's theory. He's a smart guy to propose something that is barely possible to test, like the mirror on a train travelling at the speed of light one. I don't believe a word he said.
"aliens"
 

Mr_Kap

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re: HSC Physics Marathon Archive

Explain the operation of solar cells with the aid of a diagram. [6 marks]
A solar cell is formed when two differently doped semiconductors are placed next to eachother. One of these semi-conductors must be doped with a group 3 element becoming a p-type semiconductor, and the other must be doped with a group 5 element becoming an n-type semi-conductor. When they are next to eachother it forms a p-n junction. Shit happens between the two regarding the electrons going into the holes of the p-type and a depletion zone forms, and because light is shone on it an electric field is formed between the two semi-conductors, making a current and shit.
 

atargainz

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A solar cell is formed when two differently doped semiconductors are placed next to eachother. One of these semi-conductors must be doped with a group 3 element becoming a p-type semiconductor, and the other must be doped with a group 5 element becoming an n-type semi-conductor. When they are next to eachother it forms a p-n junction. Shit happens between the two regarding the electrons going into the holes of the p-type and a depletion zone forms, and because light is shone on it an electric field is formed between the two semi-conductors, making a current and shit.
6/6 nice
 

Mr_Kap

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Does my response have the right idea though if i explained it better?? (sorry it was 11pm and i coudln't be fucked answering a whole 6 marker)
 

atargainz

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Does my response have the right idea though if i explained it better?? (sorry it was 11pm and i coudln't be fucked answering a whole 6 marker)
- Solar cell converts solar energy --> electrical energy
- N-type is thin and transparent (top layer) so that photons of sunlight can travel through N-type and hit the junction
- P/N junction and subsequent diffusion of majority charge carriers
- Set up of electric field and establishment of Depletion region (this ensures junction acts as a diode -- current can only flow one way (Really important and explains why Solar Cells produce DC, not AC)
- Light of appropriate frequency hits junction, creates electron-hole pairs
- Electrons and holes can only travel one way (electrons from P --> N and Holes N --> P due to electric field)
- Electrons travel through external circuit, do work on a load (light globe for example) and then recombine with a hole as they re-enter the P-type SC.


Make sure you are able to draw a quick diagram of a Solar Cell, diagrams always aid in explaining complicated concepts, even if the question doesnt necessarily ask for a diagram they are generally included in the higher-level responses from the higher-level students.
This is what I would talk about. Still unsure where the photoelectric effect comes into play or if it does at all.
 

zachary99

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Does my response have the right idea though if i explained it better?? (sorry it was 11pm and i coudln't be fucked answering a whole 6 marker)
too good mate, just add that the electron emitted passes its energy to a load in the external circuit e.g a light bulb
 

Mr_Kap

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This is what I would talk about. Still unsure where the photoelectric effect comes into play or if it does at all.
as light provides the energy for electrons to be continually removed from the n-type. The current would not remain if there was no light. Initially the electric field would be set up as the electrons move in the holes but then nothing would happen
 

astroman

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3marks - Q: Describe how the value of a metre can be calculated through an understanding of the speed of light.
 
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atargainz

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3marks - Q: Describe how the value of a metre can be calculated through an understanding of the speed of light.
The current definition of a standard metre uses the constancy of the speed of light in a vacuum alongside the definition of 1 second to create a distant measurement system that is consistent with the idea of space-time. As such, 1 metre is equivalent to how far light travels in a vacuum during 1/3x10^8 of a second
 

astroman

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re: HSC Physics Marathon Archive

What order is everyone doing the exam tomorrow?
 
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