VCE Physics Question Thread!

[chantelle.salisbury]

Can someone please answer this question.
Describe how matter is converted to energy by nuclear fusion in the Sun.
thank you

umm... is this on the study design? if so i better be looking it up!

i have a photoelectric q. that im stuck on
c. evaluate a value for W if the most energetic electrons have an energy of 1.9ev, and the incident light has a wavelength of 4.14*10^7m.
d. calculate the de broglie wavelength of 1.9eV electrons.

the ans.
c. 1.1eV - the incident photons have an energy of 3ev E=hc/wavelength hence, W=1.1
d. 8.9*10^10m - find momentum, then use wavelength =h/p

can anyone help here? thankyou

[Syedali_]

I need some clarification in regards to some line of best fit question

Do you just approximate it or is there an actual method to draw it ?

[chantelle.salisbury]

I need some clarification in regards to some line of best fit question

Do you just approximate it or is there an actual method to draw it ?

i would wait till someone else replied to this... but what i have been told by my teacher and at colin hopkins lecture is to ensure that you go through two points that you plot (obviously the most suitable ones depending on the question)! also use a see-through / clear ruler so that you can see whereabouts the line of best fit would be placed most correctly..

[jstrauss]

umm... is this on the study design? if so i better be looking it up!

i have a photoelectric q. that im stuck on
c. evaluate a value for W if the most energetic electrons have an energy of 1.9ev, and the incident light has a wavelength of 4.14*10^7m.
d. calculate the de broglie wavelength of 1.9eV electrons.

the ans.
c. 1.1eV - the incident photons have an energy of 3ev E=hc/wavelength hence, W=1.1
d. 8.9*10^10m - find momentum, then use wavelength =h/p

can anyone help here? thankyou

So total energy equals planks constant * frequency of light and f=c/lambda so E=hc/lambda (wavelength). Therefore you have the total energy. E = Ek + W, where E total energy and Ek is kinetic energy. So, (4.14x10^-15)(3x10^8) / 4.14x10^7 = 3 eV. Therefore, 3 = 1.9 + W, W= 1.1

Wavelength = constant / momentum as the answer states.  Using a derived fromula, p = v(2mEk) and coverting the 1.9 eV to J, p = 7. 44 x 10^-25. Therefore wavelength = 8.9 x 10^-10

[chantelle.salisbury]

So total energy equals planks constant * frequency of light and f=c/lambda so E=hc/lambda (wavelength). Therefore you have the total energy. E = Ek + W, where E total energy and Ek is kinetic energy. So, (4.14x10^-15)(3x10^8) / 4.14x10^7 = 3 eV. Therefore, 3 = 1.9 + W, W= 1.1

Wavelength = constant / momentum as the answer states.  Using a derived fromula, p = v(2mEk) and coverting the 1.9 eV to J, p = 7. 44 x 10^-25. Therefore wavelength = 8.9 x 10^-10

awesome thankyou alot...

[smiley123]

Hi everyone! I'm really confused about the right hand rule. Can someone please explain why the right hand rule is different for the green conductors when they're exactly the same? The only difference is the direction of the current of the conductor that they are parallel to, but how does this affect the direction of magnetic field for the green conductor?

[Bri MT]

Hi everyone! I'm really confused about the right hand rule. Can someone please explain why the right hand rule is different for the green conductors when they're exactly the same? The only difference is the direction of the current of the conductor that they are parallel to, but how does this affect the direction of magnetic field for the green conductor?

Ok, so the difference is that the magnetic field next to them is opposite in direction. Therefore the force is opposite in direction.

Draw more circle around the neighbouring wire if you cant see the direction of the magnetic field through the green one

[TooLazy]

Does anyone know if we can use pencil for diagrams and graphs?

Like drawing a magnetic field, or plotting a graph for the photoelectric effect with a line of best fit.

[princessofpersia]

Does anyone know if we can use pencil for diagrams and graphs?

Like drawing a magnetic field, or plotting a graph for the photoelectric effect with a line of best fit.

Yes we can

[BlinkieBill]

Hey
just wanted to confirm that relativistic mass isnt in the course?

[Bri MT]

Hey
just wanted to confirm that relativistic mass isnt in the course?

It's not, but the formula also isn't difficult you just use the Lorentz transformation so if it reassures you you can take a cm to write it down

[chantelle.salisbury]

Can someone please answer this question.
Describe how matter is converted to energy by nuclear fusion in the Sun.
thank you

Did anyone end up replying to this?
i would use the formula that E=mc^2, tho not entirely sure how to 'describe'.

[Bri MT]

Did anyone end up replying to this?
i would use the formula that E=mc^2, tho not entirely sure how to 'describe'.

If you are doing the fission/fusion extended study,  you should refer to the 4 fusion formulae & list the energy released by each one. Also provide an overall energy release, and describe mass-energy equivalence

[TooLazy]

It's not, but the formula also isn't difficult you just use the Lorentz transformation so if it reassures you you can take a cm to write it down

Relativistic mass is on the course

[Bri MT]

Relativistic mass is on the course

Where?
"Einstein’s theory of special relativity
•    describe Einstein’s two postulates for his theory of special relativity that:
–    the laws of physics are the same in all inertial (non-accelerated) frames of reference
–    the speed of light has a constant value for all observers regardless of their motion or the motion of the source
•    compare Einstein’s theory of special relativity with the principles of classical physics
•    describe proper time (t0 ) as the time interval between two events in a reference frame where the two events
occur at the same point in space
•    describe proper length (L0 ) as the length that is measured in the frame of reference in which objects are at rest
•    model mathematically time dilation and length contraction at speeds approaching c using the equations:
•    explain why muons can reach Earth even though their half-lives would suggest that they should decay in the
outer atmosphere."

I can't find it in the study design?
The Edrolo person also said it isn't on the course this year as well