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Can someone check if these are correct don't have the markscheme watch

1. So i've been looking through this past paper and just want to see if the questions i'm not so confident are correct, as i don't have the mark scheme as ou have to pay. It's question 1

For 1a) i got 600m/s(although this seems stupid) frequency i did v=flamda fo f=v/lamda =600/0.6=1000hz

1b)1 i got 1.2m and 1.8m
for 1b)2 I said it varies depending if theres been constructive interference creating a antinnode or destructive creating a node, but it is consistent pattern.

I said it isnt the same for the progressive wave want really sure as to why

For 1C i wasnt sure

Thanks!
2. (Original post by hazbaz)
For 1a) i got 600m/s(although this seems stupid) frequency i did v=flamda fo f=v/lamda =600/0.6=1000hz
velocity = wavelength/period. What's the value of wavelength, what's the value of the period?

1b)1 i got 1.2m and 1.8m
Right. Just in case you didn't realise, there are nodes every , i.e. 0.3m.

for 1b)2 I said it varies depending if theres been constructive interference creating a antinnode or destructive creating a node, but it is consistent pattern.
Generally, right. If you want to be more specific you can say that the value of amplitude is of the form where is the maximum amplitude (the amplitude at antinodes).

I said it isnt the same for the progressive wave want really sure as to why
You're right. In the progressive wave each point of the string oscillates up and down with the same amplitude. In standing wave there is interference, and at some points the interference is completely destructive (these are nodes) - so they do not oscillate at all.
3. (Original post by jaroc)
velocity = wavelength/period. What's the value of wavelength, what's the value of the period?

Right. Just in case you didn't realise, there are nodes every , i.e. 0.3m.

Generally, right. If you want to be more specific you can say that the value of amplitude is of the form where is the maximum amplitude (the amplitude at antinodes).

You're right. In the progressive wave each point of the string oscillates up and down with the same amplitude. In standing wave there is interference, and at some points the interference is completely destructive (these are nodes) - so they do not oscillate at all.
Ah right thanks i'll do those corrections and repost! would you possibly be able to help with question 2 as well?

For question 1 im not really too sure on the period i know its calcualted as 1/frequency but we havnt got teh frequency is it simply just the time? so 0.0030
4. (Original post by hazbaz)
Ah right thanks i'll do those corrections and repost! would you possibly be able to help with question 2 as well?

For question 1 im not really too sure on the period i know its calcualted as 1/frequency but we havnt got teh frequency is it simply just the time? so 0.0030
If you look at consecutive graphs of the wave you'll see that the bottom graph looks exactly like the first one. The time corresponding to those two 'snapshots' is 4x0.0030s. This is the period. Can you see why?

Then you can calculate frequency.

5. (Original post by jaroc)
If you look at consecutive graphs of the wave you'll see that the bottom graph looks exactly like the first one. The time corresponding to those two 'snapshots' is 4x0.0030s. This is the period. Can you see why?

Then you can calculate frequency.

ah riht so the speed is going to be 0.6/4(0.003)=50 and the frequency is 1/period which =83.3?

I think i've more or less got question 2 now it's just 2d i'm stuck on and for question 3a do i use sin1/sin2 =c1/c2 or do i use n1sin1=n2sin2 how can you tell?
6. (Original post by hazbaz)
ah riht so the speed is going to be 0.6/4(0.003)=50 and the frequency is 1/period which =83.3?
Correct.

I think i've more or less got question 2 now it's just 2d i'm stuck on
Try to propose some solution, I can have a look at it tomorrow in the evening as I have some work to do tonight However, if anyone is able to help sooner than I am, feel free to do that.

for question 3a do i use sin1/sin2 =c1/c2 or do i use n1sin1=n2sin2 how can you tell?
These formulas are equivalent.

Spoiler:
Show

You can use whichever you like. Here the formula is more useful as you're given the values of the refractive indices, not the speeds.
7. (Original post by jaroc)
Correct.

Try to propose some solution, I can have a look at it tomorrow in the evening as I have some work to do tonight However, if anyone is able to help sooner than I am, feel free to do that.

These formulas are equivalent.

Spoiler:
Show

You can use whichever you like. Here the formula is more useful as you're given the values of the refractive indices, not the speeds.
Thanks for all the help standing waves and refractive index angle of incdeicne arnt my strong point . REally appreciate it!

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