Physics Predictions/Thoughts (5 Viewers)

[iheartcookies1012]

1 second is time it takes for 9,192,631,770 vibrations between the two hyperfine levels of the ground state in cesium-133. we dont need to know it for hsc

really? how abt one ampere relating to the parallel conductors thingy

 

[Rattlehead15]

Its crucial you have an in-depth knowledge of something as important as the quantisation of energy ESP. for discussion question, its literally a wild card in the sense you can weave it into so much Mod 7 questions while maintaining relevance/brevity due to how fundamental it is.

HSC answers aren't there to give you the "best answer" but moreso a vague/general descriptor of what consists of a good answer. You should make sure you're responses meet the following points:

- Concise (Don't waffle, this isnt Common Mod)
- Cites mathematical laws
- Utilises scientific jargon
- Clear (having clarity is just as important to being concise, be specific)

Will do, but problem is in some answers I say way too much and others not enough. Caused me to not finish the paper I did today and lost 7 marks on unattempted questions but ig I gotta pay closer attention to being concise and allocating certain lengths of responses appropriate to how many marks there are

 

[Trippzy]

yo can someone give some tips for mcq, I can do alright in written responses but I can never get good marks for mcq

 

[SB257426]

really? how abt one ampere relating to the parallel conductors thingy

yeah im pretty sure we dont need to know it.

The ampere thing we need to know. Especially with its relation to newtons third law.

 

[iheartcookies1012]

yeah im pretty sure we dont need to know it.

The ampere thing we need to know. Especially with its relation to newtons third law.

newtons thrid law? i mean the one whre its like one ampere is the current that must flow through two infinite parallel current conductors positioned one metre apart in a vacuum such that the force experienced is (some value i forogot) per unit of length. or its like 1 coloumb of charge moving past per second or 1/1.602...*10^-19 electrons worth of charge LOL

 

[carrotsss]

yo can someone give some tips for mcq, I can do alright in written responses but I can never get good marks for mcq

idk the main things are just narrowing down like crossing out every obviously incorrect answer since that usually gets you down to only a couple and then just carefully/patiently consider between the two remaining options. i think a lot of the time we don’t really give m/c proper thought and end up just skipping through it which contributes a lot to doing worse in it

 

[ExtremelyBoredUser]

Sorry if you actually explained this already but I feel like I'm still missing the point here. I understand that the number of available energy levels has to be limited because quantum theory means that there has to be an integer amount of photons with that energy, but why does it have to be low? Or is the fact that it's low more to do with the intensity of radiation and peak wavelength of radiation is dependent on the temperature of the radiator and bc it releases a continuous spectrum of light across all wavelengths the intensity has to shoot down dramatically from it's peak to zero?

Refer back to my post again, it's a probabilistic thing. A photon at very low wavelength is one with very high frequency and as frequency is prop to energy, it means that for an oscillator to emit radiation at that range, it requires an excessive amount of energy which is distributed as a discrete quantity i.e an energy packet which is very unlikely.


This is why the classical models failed since it assumes that the continuous nature of light and this means that these energy outputs can be reached over time. It also means that in theory energy transmitted can be unbounded which violates conservation laws and this was the UV catastrophe, in that Rayleigh Jeans law and the classical models failed to accurately describe the energy distribution of a blackbody.

The quantised nature of light elegantly resolves this dilemma as it means that an excessive amount of energy must be emitted in the form of an energy packet instantaneously, hence the blackbody oscillator must already have an excessive amount of energy as to radiate at very low wavelengths which by intuition is extremely rare.

Does this make sense from an intuitive level? I assume that's what you want rather than mathematical explanation. Please consider Rayleighs curve, Planck's law, wavelength vs intensity graph of a blackbody etc. when thinking. Planck's law E = hf implies the energy frequency relationship.

 

[carrotsss]

Refer back to my post again, it's a probabilistic thing. A photon at very low wavelength is one with very high frequency and as frequency is prop to energy, it means that for an oscillator to emit radiation at that range, it requires an excessive amount of energy which is distributed as a discrete quantity i.e an energy packet which is very unlikely.


This is why the classical models failed since it assumes that the continuous nature of light and this means that these energy outputs can be reached over time. It also means that in theory energy transmitted can be unbounded which violates conservation laws and this was the UV catastrophe, in that Rayleigh Jeans law and the classical models failed to accurately describe the energy distribution of a blackbody.

The quantised nature of light elegantly resolves this dilemma as it means that an excessive amount of energy must be emitted in the form of an energy packet instantaneously, hence the blackbody oscillator must already have an excessive amount of energy as to radiate at very low wavelengths which by intuition is extremely rare.

Does this make sense from an intuitive level? I assume that's what you want rather than mathematical explanation. Please consider Rayleighs curve, Planck's law, wavelength vs intensity graph of a blackbody etc. when thinking. Planck's law E = hf implies the energy frequency relationship.

What’d u get in physics again

 

[ExtremelyBoredUser]

What’d u get in physics again

92 pre sure, could've done better but b6 is a b6 but I'm doing physics at uni as well so this stuffs also in my mind

 

[ExtremelyBoredUser]

Will do, but problem is in some answers I say way too much and others not enough. Caused me to not finish the paper I did today and lost 7 marks on unattempted questions but ig I gotta pay closer attention to being concise and allocating certain lengths of responses appropriate to how many marks there are

It's time to be exam savy. Get a jist of what each mark entails you to write and how to write. What does a 4 mark short answer expect you to write? What does a long answer response expect and how would B6ers respond etc. Go to hsc papers and just read the marking criteria for the sols since it's the similar type of guidelines hsc markers will follow. Be harsh in your marking, punish every mistake you make in your answers and learn from it.

 

[ExtremelyBoredUser]

Btw is physics tomorrow? Or today? @carrotsss

 

[CamdenCeccato]

Btw is physics tomorrow? Or today? @carrotsss

tomorrow

 

[SB257426]

newtons thrid law? i mean the one whre its like one ampere is the current that must flow through two infinite parallel current conductors positioned one metre apart in a vacuum such that the force experienced is (some value i forogot) per unit of length. or its like 1 coloumb of charge moving past per second or 1/1.602...*10^-19 electrons worth of charge LOL

Yeah its the force per unit length definition

 

[yleeey]

anyone know what formula to use for this question?

 

[abelsj01]

how likely is an ac induction motor question for this yrs paper

View attachment 41318

anyone know what formula to use for this question?

not entirely sure but positive work is done to move an object into higher orbits, so maybe use the formula for total energy which is E = -GMm/2r at both radii and then subtract to find the difference?

 

[abelsj01]

not entirely sure but positive work is done to move an object into higher orbits, so maybe use the formula for total energy which is E = -GMm/2r at both radii and then subtract to find the difference?

i tried it and i got the right answer when i used r = 6800km and 42000km but not when i used r = 6800km + radius of the earth etc. i thought the radius was actually the radius of the earth + the altitude; is this not true?

 

[Rattlehead15]

hence the blackbody oscillator must already have an excessive amount of energy as to radiate at very low wavelengths which by intuition is extremely rare.

OHHH ty I get it now. Its rare for anything to emit a single photon with that much energy/that high frequency, whereas waves can just achieve the energy by transferring it continuously over time. Photons need to transfer it in one packet which is rare to happen.

 

[esybeast]

not entirely sure but positive work is done to move an object into higher orbits, so maybe use the formula for total energy which is E = -GMm/2r at both radii and then subtract to find the difference?

why can't u find the find using change in GPE ie dU = GMm(1/ri-1/rf)

 

[Rattlehead15]

punish every mistake you make in your answers and learn from it

Yeah Ive been doing that and it really helps. I pushed my past paper marks up from mid band 5 to low band 6. Just gotta hope the paper is good for me on the day, ie no polarisation

 

[ms_grape_taco]

what were the 2 postulates from plancks discovery?