Angle of refraction snells law

[kthejohnster]

im having difficulty understanding how light leaves a prism mainly because I am not sure about what angles we are talking about when we say angle of refraction/incidence.
Lets say for example light hits a triangular prism leg at a 90 degree angle (incidence = 90 deg?) and the prism has index of 1.4 compared to surrounding air's 1.0 using snells law would get an angle of refraction. Now I am getting lost trying to find the angle that it strikes the hypotenuse and the angle that it leaves the prism. how would i use snells law again?

 

[sankalpmittal]

im having difficulty understanding how light leaves a prism mainly because I am not sure about what angles we are talking about when we say angle of refraction/incidence.
Lets say for example light hits a triangular prism leg at a 90 degree angle (incidence = 90 deg?) and the prism has index of 1.4 compared to surrounding air's 1.0 using snells law would get an angle of refraction. Now I am getting lost trying to find the angle that it strikes the hypotenuse and the angle that it leaves the prism. how would i use snells law again?

All I know is that when a monochromatic ray of light (let's say) enters from medium 1 to medium 2 then ,
Refractive index of medium 2 or ₁μ₂ = angle of incidence in medium 1 / angle of incidence in medium 2

Representation : ₁μ₂= μ₂/μ₁
Yes , we represent refractive index of medium 2 with respect to medium 1 as ₁μ₂

Always remember this to avoid confusion.

angle of refraction/incidence becomes inverse refractive index.

In your case
1.4 = sin 90^o/sin r

And please I cannot understand what you mean by leg angle or etc etc ? Are you taking a right angled prism ? Please give me a diagram of your question.

 

[Doc Al]

Lets say for example light hits a triangular prism leg at a 90 degree angle (incidence = 90 deg?) and the prism has index of 1.4 compared to surrounding air's 1.0 using snells law would get an angle of refraction. Now I am getting lost trying to find the angle that it strikes the hypotenuse and the angle that it leaves the prism. how would i use snells law again?

I assume you mean that the light hits perpendicular to the first surface. Since angles (in Snell's law) are measured from the normal, that would mean that the angle of incidence is 0°, not 90. To find the angle that the light hits the other side of the prism, you'll need to use a bit of geometry. Figure out the new angle of incidence and apply Snell's law to find the angle the light makes upon leaving the prism.

 

[emailanmol]

Angle of incidences and refraction(and even reflection) are always measured from the normal of refracting surface(or reflecting surface)

Remember, angle of incidence, refraction and normal always lie in the same plane.

As Doc Al pointed, since the ray is perpendicular to surface, it is actually parallel to normal and therefore angle of incidence is 0 degrees.


For further calculation you will need the angle of prism and some simple applications of geometry trigonometry