Refraction - A Level Physics, Require HELP!

http://prntscr.com/7cp0s6 This is the question I need help on 3bi) I've done ii) which gave me 74.96 degrees. I'm unsure on 3bi though!

Reply 1

AndyW123

Original post by 1017bsquad

http://prntscr.com/7cp0s6 This is the question I need help on 3bi) I've done ii) which gave me 74.96 degrees. I'm unsure on 3bi though!

From what I can see it is just a triangle with angles 85, 30, and i.
So that would make i = 180 - 30 - 85 = 65 degrees?

Reply 2

1017bsquad

Original post by AndyW123

From what I can see it is just a triangle with angles 85, 30, and i.
So that would make i = 180 - 30 - 85 = 65 degrees?

Ahh **** lol my bad, I didn't know whether to take the top left angle as 85 degrees. Well cheers man thanks for that I tried to use equations and all sorts haha!

Reply 3

AndyW123

Original post by 1017bsquad

Ahh **** lol my bad, I didn't know whether to take the top left angle as 85 degrees. Well cheers man thanks for that I tried to use equations and all sorts haha!

No worries :smile:

Just remember that for a reflection the angle of incidence is always the same as the angle of refraction. Obviously this is not the same when actually being refracted.

Reply 4

Lilli1997

Original post by 1017bsquad

http://prntscr.com/7cp0s6 This is the question I need help on 3bi) I've done ii) which gave me 74.96 degrees. I'm unsure on 3bi though!

ai) cladding
aii) Critical angle= Sin^-1(1.41/1.46)=74.96
bi) 180-30-85=65 (The 85⁰ is because angle of incidence=angle of reflection) (180⁰ as its a triangle)
bii) use n₁sinx₁=n₂sinx₂
1.46sin65=1.41sinx₂
x₂=Sin^-1((1.46sin65)/1.41)
=69.79
=70⁰

hopefully makes sense