Snell's law

  • Thread starter Az83
  • Start date
  • #1
8
0
For Snell's law n2sin(theta2)=n1sin(theta1), I know that air has an index of refraction of approximately 1. But how do I find the actual value for the index of refraction if I know the temperature jump and pressure? I know that from what I am given, I can find the densities of the air, but then how do I use the densities to find the index of refraction?
 

Answers and Replies

  • #2
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,121
160
A Google search on
air "refractive index"
led me here:
http://www.strw.leidenuniv.nl/~mathar/progs/prWaterWeb.html [Broken]
Calculates (n-1) depending on temperature, pressure, humidity, and even CO2 content of the atmosphere!

Do you happen to have a particular application or use in mind? Eg., ray tracing calculation, atmospheric distortion, solving a homework problem, other?
 
Last edited by a moderator:
  • #3
olgranpappy
Homework Helper
1,271
3
well. I think you could look up the dielectric constant ([itex]\epsilon[/itex], where [itex]n^2=\epsilon[/itex]) at different densities. but also, if you know the dielectric constant at some given number density ([itex]n_1[/itex]) then to find it at a different density you could use
[tex]
\frac{\epsilon(n_2)-\epsilon(n_2)}{\epsilon(n_1)-1}=\frac{n_2-n_1}{n_1}
[/tex]

...and, sorry for using the symbol n for two different things... my bad, in the equation it is number density, not index of refraction
 
Last edited:
  • #4
8
0
this question is for a homework problem. It seems that every source I look at, the dielectric constant for air at 1 atm is 1.00059. Is this value safe to assume for all temperatures?
 
  • #5
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,121
160
this question is for a homework problem. It seems that every source I look at, the dielectric constant for air at 1 atm is 1.00059. Is this value safe to assume for all temperatures?

No, it will change with temperature and pressure. The denser the air, the higher the value.
 
  • #6
8
0
Is there an equation that relates the density to the index of refraction?
 
  • #7
olgranpappy
Homework Helper
1,271
3
i gave it to you
 
  • #8
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,121
160
Is there an equation that relates the density to the index of refraction?

You can do pretty well by assuming (n-1) is proportional to the air density.
 

Related Threads on Snell's law

  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
893
  • Last Post
Replies
2
Views
738
  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
10
Views
3K
  • Last Post
Replies
15
Views
3K
Replies
13
Views
2K
Replies
7
Views
657
Replies
8
Views
2K
Replies
10
Views
2K
Top