Jennifer50
Badges: 4
Rep:
?
#1
Report Thread starter 3 years ago
#1
Why does the relative refractive index for speeds between 2 materials need to be lower than 1 for TIR to occur, and how would it be like for refractive indices instead of speed?
0
reply
pri12321
Badges: 3
Rep:
?
#2
Report 3 years ago
#2
(Original post by Jennifer50)
Why does the relative refractive index for speeds between 2 materials need to be lower than 1 for TIR to occur, and how would it be like for refractive indices instead of speed?
TIR is total internal reflection, not refraction. It happens when the angle of incidence is greater than the critical angle, from a more optically dense material to a less optically dense one.
I'm not sure what you are asking about speeds?
0
reply
voltz
Badges: 6
Rep:
?
#3
Report 3 years ago
#3
(Original post by TheBride)
TIR is total internal reflection, not refraction. It happens when the angle of incidence is greater than the critical angle, from a more optically dense material to a less optically dense one.
I'm not sure what you are asking about speeds?
Exactly what he said, and regarding the speed, the wave speeds up as it is refrated from a more dense to less dense medium hence the angle of refraction is greater than the angle of incidence
0
reply
Jennifer50
Badges: 4
Rep:
?
#4
Report Thread starter 3 years ago
#4
(Original post by voltz)
Exactly what he said, and regarding the speed, the wave speeds up as it is refrated from a more dense to less dense medium hence the angle of refraction is greater than the angle of incidence
It was a question on the aqa as physics paper 2 specimen paper
0
reply
natninja
Badges: 21
Rep:
?
#5
Report 3 years ago
#5
(Original post by Jennifer50)
Why does the relative refractive index for speeds between 2 materials need to be lower than 1 for TIR to occur, and how would it be like for refractive indices instead of speed?
We'll start with Snell's law n_isin(\theta_i)=n_rsin(\theta_r  )

if we set the beam to be the minimum angle of incidence that produces TIR then \theta_r = 90

this means that n_isin(\theta_i) = n_r

since 0 \leq sin(\theta) \leq 1, 0 \leq \theta \leq 90

\frac{n_r}{n_i} \leq 1
0
reply
natninja
Badges: 21
Rep:
?
#6
Report 3 years ago
#6
(Original post by Jennifer50)
Why does the relative refractive index for speeds between 2 materials need to be lower than 1 for TIR to occur, and how would it be like for refractive indices instead of speed?
Also the speed of light in a material is related to the refractive index by

n = \frac{c}{v} where c is the speed of light in vacuo and v is the speed of light in the medium.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Sheffield Hallam University
    Get into Teaching in South Yorkshire Undergraduate
    Wed, 26 Feb '20
  • The University of Law
    Solicitor Series: Assessing Trainee Skills – LPC, GDL and MA Law - London Moorgate campus Postgraduate
    Wed, 26 Feb '20
  • University of East Anglia
    PGCE Open day Postgraduate
    Sat, 29 Feb '20

People at uni: do initiations (like heavy drinking) put you off joining sports societies?

Yes (476)
66.39%
No (241)
33.61%

Watched Threads

View All