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Help with OCR AS physics please.

Hello,

I was going through this physics paper http://www.ocr.org.uk/Images/58130-question-paper-unit-g482-electrons-waves-and-photons.pdf

I got stuck on question 4Ei and ii. I know what the answer is, but it didn't help me figure out how to answer it. I think my teacher hasn't covered this yet so i had to learn waves stuff my self, it may be because I taught my self poorly that I don't know how to start off :confused:

Thank you!

(edited 9 years ago)

Reply 1

Puddles the Monkey

Original post by corpeal

Thank you!

Heya, I'm going to put this in the physics forum for you as you should get more responses there.

You should also check out the forum to see if there's any other threads there which might be helpful to you!

http://www.thestudentroom.co.uk/forumdisplay.php?f=372

Reply 2

MrMatheson

The intensity of a wave is proportional to the amplitude squared.

That means that when the amplitude is 2 the intensity is I, when the amplitude is 3 we need to know the new intensity. This is the ratio of the amplitudes squared. i.e. 9/4=2.25

Reply 3

MrMatheson

This may help too: https://www.youtube.com/watch?v=dV7WqWIMl0o&index=5&list=PLlDtVvefFYT9NxoJ70Ns7Htg9Um2gUPRP

Reply 4

MrMatheson

For part ii) you look at the resultant of the two waves (principle of superposition). If the amplitude is now 1 rather than the original value of 2 or 3 you can use this to find the final intensity I.

Reply 5

exoticmedgirl_2017

Calculate the de Broglie wavelength associated with each of the
following :
(a) A bullet of mass 25 g moving at a velocity of 280 m s-1. : 9.47*10^-35m
(b) An sprinter of mass 90 kg moving at a velocity of 11 m s-1.: 6.70*10^-37m
(c) An electron of mass 9.11 x 10-31 kg moving at a velocity of 2.0 x 10^7 m s-1. : 3.64*10^-16m

Are my answers right??