Why Light Doesn't Deviate When Entering Semi-Circular Glass?

In summary, the light ray will not be deviated when it enters a semi circular glass block. The angle of incidence is the same at both the surface of the glass and the surface of the air, so the ray of light will pass straight through.
  • #1
Mphisto
23
0

Homework Statement


Well, this is not really a homework question but something I wanted to find out. Basically, Why there is no deviation of light ray when it enters a semi circular glass block?


Homework Equations





The Attempt at a Solution


I thought light ray would not be deviated only when it enters another medium perpendicular to boundary. So why would it not be deviated when it enters the a semi circular glass block?

Thank you :smile:
 
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  • #2


Hi, Mphisto,

The light ray will deviate if it enters at an angle with respect to the surface normal. Why do you think it will not?

ehild
 
  • #3


ehild said:
Hi, Mphisto,

The light ray will deviate if it enters at an angle with respect to the surface normal. Why do you think it will not?

ehild

I don't get your post...
 
  • #4


Mphisto said:
Basically, Why there is no deviation of light ray when it enters a semi circular glass block?
How is the light entering the block? What angle is it making with the normal to the surface?
 
  • #5


Doc Al said:
How is the light entering the block? What angle is it making with the normal to the surface?

http://t2.gstatic.com/images?q=tbn:ANd9GcRhvx6-lH4b3Dpe1otCjmmVHn_bcsWOpLUnEf-_A3IhQQON_YG0 [Broken]
Taken from google, as you can see the incident ray passes straight through the glass block
 
Last edited by a moderator:
  • #6


Mphisto said:
Taken from google, as you can see the incident ray passes straight through the glass block
At the first surface (air to glass), the angle with the normal is zero so it passes straight through. Is that what you mean? (The ray of light is directed along the radius, so it is normal to the surface.)

Of course it undergoes refraction when it leaves the block.
 
  • #7


Doc Al said:
At the first surface (air to glass), the angle with the normal is zero so it passes straight through. Is that what you mean? (The ray of light is directed along the radius, so it is normal to the surface.)

Of course it undergoes refraction when it leaves the block.

"angle with the normal is zero"? shouldn't the light ray be refracted at the first surface? (air to glass)
 
  • #8


Mphisto said:
"angle with the normal is zero"?
That's correct.
shouldn't the light ray be refracted at the first surface? (air to glass)
What's the angle of incidence?
 
  • #9


Doc Al said:
That's correct.

What's the angle of incidence?

I am not sure... since it's curved i don't know how the normal would be placed there
 
  • #10


Mphisto said:
I am not sure... since it's curved i don't know how the normal would be placed there
Note that the incoming light ray is aimed along the radius of the circle and is thus normal to the surface. (Imagine a tangent line to the semi-circle drawn at the point where the light enters--take that as the surface.)
 
  • #11


Doc Al said:
Note that the incoming light ray is aimed along the radius of the circle and is thus normal to the surface. (Imagine a tangent line to the semi-circle drawn at the point where the light enters--take that as the surface.)

So basically the normal of first surface is like a tangent line to the semi-circle? am I right to say that?
 
  • #12


Mphisto said:
So basically the normal of first surface is like a tangent line to the semi-circle? am I right to say that?
No. The normal is perpendicular to the tangent line.
 
  • #13


Doc Al said:
No. The normal is perpendicular to the tangent line.

Oh ok, I got it :biggrin:

Thank you!
 

1. Why doesn't light deviate when entering semi-circular glass?

Light is an electromagnetic wave that travels in a straight line. When it enters a medium like glass, it slows down and changes direction, but it does not deviate from its original path unless it encounters a different medium or obstacle.

2. How does the shape of glass affect the deviation of light?

The shape of glass, specifically in a semi-circular form, does not have a significant impact on the deviation of light. As mentioned before, light will only change direction when it encounters a change in medium or an obstacle. The shape of the glass does not alter the properties of light itself.

3. What about the angle of incidence? Does it affect light deviation in semi-circular glass?

The angle of incidence, which is the angle at which light enters the glass, does play a role in light deviation. However, in the case of semi-circular glass, the angle of incidence is not a factor as the light enters at a perpendicular angle.

4. Is there any difference in light deviation when entering semi-circular glass compared to other shapes?

No, the shape of the glass does not affect the deviation of light. As long as the medium remains the same, the light will continue to travel in a straight line until it encounters a different medium or obstacle.

5. Can light deviate in semi-circular glass under certain conditions?

Under normal circumstances, light will not deviate when entering semi-circular glass. However, if the glass is coated with a thin film or has impurities that cause a change in the medium, light may deviate slightly. But this deviation would be minimal and not noticeable to the naked eye.

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