Light passing through the normal of a surface

In summary: In a sense it is like a driven electrical or mechanical circuit, where the driving term is A sin(wt). No matter what the circuit is, the frequency is unchanged.thanks Bob you are a great help :smile:
  • #1
zero_kilo
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When light passes from one medium to other there is refraction but at the normal to the surface no refraction why? We know refraction occurred due to change in speed of light in the medium.

Also why frequency of light do not change in going from one medium to other medium (eg from air to glass or vice-versa)

thanks
 
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  • #2
There usually always is both refraction and reflection for normal incidence. For an index of refraction n=1.5 from air (n=1), the fraction reflected is

F = (n-1)2/(n+1)2 = 0.04

The frequency of the light radiation is conserved, but in the medium, atoms absorb and re-radiate the light, causing a delay or reduction of the velocity.
Bob S
 
  • #3
Bob S said:
There usually always is both refraction and reflection for normal incidence. For an index of refraction n=1.5 from air (n=1), the fraction reflected is

F = (n-1)2/(n+1)2 = 0.04

The frequency of the light radiation is conserved, but in the medium, atoms absorb and re-radiate the light, causing a delay or reduction of the velocity.
Bob S

thanks Bob :smile:

i understand what you said but when drawn a normal to the incident light its straight.At the normal let's have an incident light (normal incident) we always draw straight in the diagram or shall we say its just a diagram and let know that there is still refraction.Refarction changes normal path.Why draw straight :biggrin:

can you please elaborate the conservation of frequency.

thanks again
 
  • #4
"Normal" means perpendicular to the surface. There are certain special angles where there is no relection of polarized light. See
http://en.wikipedia.org/wiki/Brewster's_angle
Bob S

re frequency: the light slows down and the wavelength gets shorter when it enters a refrective medium, but frequency is unchanged. In a sense it is like a driven electrical or mechanical circuit, where the driving term is A sin(wt). No matter what the circuit is, the frequency is unchanged.
 
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  • #5
thanks Bob you are a great help :smile:

but this is still my question:

For a ray of light incident normally, there is no change in the direction of its path

Why? Is not there are a refraction when it passes from one medium to another? Refraction changes direction of path.:confused:

thanks
 
  • #6
Consider a series of wavefronts incident on a medium at an angle. The rate (eg. 1 per second) at which the waves arrive at and leave the surface of the medium must be the same. Hence frequency is conserved and the wavelength changes.

If we represent the wavefront by a line then part of the wavefront in medium 1 has one wavelength a and in in medium 2 it has wavelegth b. The line has to be continuous (there is no break) so the angle with respect to the interface changes.

However, if the waves are incident normal to the interface then the change in wavelength can be accommodated without changing the angle. Indeed, why would they bend one way and not another?
 
  • #7

What is "light passing through the normal of a surface"?

"Light passing through the normal of a surface" refers to the process of light traveling through a surface at a perpendicular angle to the surface's orientation. The normal of a surface is an imaginary line that is perpendicular to the surface at a specific point.

Why is the normal of a surface important when considering light passing through it?

The normal of a surface is important because it determines the angle at which light will pass through the surface. This angle affects how much of the light is reflected, absorbed, or transmitted through the surface.

How is the angle of incidence related to the normal of a surface?

The angle of incidence is the angle at which light strikes a surface. The angle of incidence is always measured in relation to the normal of the surface, with a 0-degree angle of incidence being parallel to the normal and a 90-degree angle of incidence being perpendicular to the normal.

What is the law of reflection and how does it relate to light passing through the normal of a surface?

The law of reflection states that when light strikes a surface, the angle of reflection will be equal to the angle of incidence, with both angles being measured in relation to the normal of the surface. This law applies to light passing through the normal of a surface as well.

How does the normal of a surface affect the refraction of light?

The normal of a surface plays a key role in the refraction of light. When light passes through a medium with a different density, the normal of the surface determines the angle at which the light will bend, also known as the angle of refraction. This angle is different from the angle of incidence due to the change in density, and the extent of the change is determined by the angle of the normal.

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