# Size of a light beam before and after Refraction

• B

## Summary:

The size of light beam is same or different before and after refraction from a medium. If same then why we can not prove from mathematical expression. If not same why?
The size of light beam is same or different before and after refraction from a medium. If same then why we can not prove from mathematical expression. If not same why?

Related Classical Physics News on Phys.org
berkeman
Mentor
Summary:: The size of light beam is same or different before and after refraction from a medium. If same then why we can not prove from mathematical expression. If not same why?

The size of light beam is same or different before and after refraction from a medium. If same then why we can not prove from mathematical expression. If not same why?
Doesn't look the same size to me...

https://cdn3.vectorstock.com/i/1000...rism-ray-rainbow-spectrum-vector-22696987.jpg • davenn and csirvi
Its helpful. . One more question is that if we take single color then the angle of deviation is same but also width of beam after refraction changes mathematically how that is physically possible ?

berkeman
Mentor
Can you post a picture or diagram of the situation you are asking about? Thanks.  Nugatory
Mentor
then the angle of deviation is same but also width of beam after refraction changes mathematically
Does it? The width of the beam is the distance along a perpendicular to the direction of travel. Look carefully at the angles that you're taking teh cosine of.... are these what you want?

Does it? The width of the beam is the distance along a perpendicular to the direction of travel. Look carefully at the angles that you're taking teh cosine of.... are these what you want?
See width represent soze of beam yes that perpendicular to the Direction of travel.
My question is when the deviation angle same why the width is variable

Can you post a picture or diagram of the situation you are asking about? Thanks. Posted the image.

Can you post a picture or diagram of the situation you are asking about? Thanks.  