Snell's Law/Refraction Flashcards
Refraction Definition
The bending of light as it travels, at an angle, from a material with one refractive index to a material with a different refractive index.
When light travels from one medium to another, for example from air to water, the light rays:
Refract (Bend)
What does it mean when light rays refract? (What changes?)
Both its speed and direction change.
What is the the surface between two mediums called?
The boundary
True or False: When a light wave crosses the boundary between two media, its speed changes.
True
How can the exact path of light as it travels from one medium to another be found, which states?
By applying Fermat’s Principle, which states that when light travels from one point to another, it follows the path that will take the least time.
When travelling from one medium to another, the path that takes the least time is not a what type of line?
Straight line
In a refraction ray diagram, what is the third ray called in addition to the incident ray and the reflected ray?
The Refracted Ray
Refracted Ray Definition
The ray that is bent upon entering a second medium.
In a refraction ray diagram, what two rays is the incident ray divided into?
One that reflects and one that refracts
True or False: Because of the additional ray, the refracted ray, there is an additional angle to keep track of.
True
What is this new angle called?
The Angle of Refraction
Angle of Refraction Definition
The angle between the normal and the refracted ray.
What happens when a light ray travels from a medium in which its speed is faster (such as air) to a medium in which its speed is slower (such as water)?
The refracted ray bends toward the normal.
What happens when a light ray travels from a medium in which its speed is slower (such as water) to a medium in which its speed is faster (such as air)?
The refracted ray bends away from the normal.
How is how much a light ray refracts determined by?
The extent of the change in the speed of light as it travels from one medium to another?
What happens when light passes from one medium to the next and the change in the speed of light becomes greater?
The angle of refraction becomes greater.
What is the speed of light in a vacuum?
3.00 x 10^8 m/2
What is the ratio of the speed of light in a vacuum to the speed of light in a given medium?
The Index of Refraction
Index of Refraction Definition
The ratio of the speed of light in a vacuum to the speed of light in a given medium.
What does “n” represent in the formula n=c/v?
The index of refraction
What does “c” represent in the formula n=c/v?
The speed of light in a vacuum
What does “v” represent in the formula n=c/v?
The speed of light in a medium
White light, which includes all the wavelengths of visible light, refracts twice when going through a prism: once when it enters the prism and again when it leaves the prism. What happens when the white light leaves the prism?
The light separated into a spectrum of colours.
What is this separation process called?
Dispersion
Dispersion Definition
The process of separating colours by refraction.
True or False: Each colour of light travels at a slightly different speed in any medium.
True
Why is the index of refraction always greater than 1? Why does the speed of light decrease?
Because the speed of light is always higher in a vacuum than in a medium; as the speed of light decreases due to the medium, the index of refraction increases.
As the index of refraction increases, what decreases?
The speed of light.
As the index of refraction decreases, what increases?
The speed of light
Snell’s Law Definition
A relationship between the path taken by a ray of light in crossing the boundary or surface of separation between two contacting surfaces and the refractive index of each.
What is the formula for index of refraction?
N=C/V
What is the formula for Snell’s Law
n1sinbeta1=n2sinbeta2
What is an example of Partial Reflection and Refraction?
When you look out a window, as you can see what is outside as well as your own reflection.
True or False: Some light reflects and some light refracts at a surface between two media that have different indices of refraction.
True
What is the phenomenon in which some light is reflected, and some light is refracted called?
Partial Reflection and Refraction
Partial Reflection and Refraction Definition
A phenomenon in which some of the light that is travelling from one medium into another is reflected and some is refracted at the boundary between the media.
What does the amount of reflection compared with the amount of refraction depend on?
The angle of incidence as well as the relative indices of refraction of the two media.
In terms of partial reflection and refraction, what happens when light travels from air into water?
-If the angle of incidence is nearly zero, most of the light penetrates the surface and very little is reflected.
-As the angle of incidence increases, more light is reflected at the surface and less light penetrates the surface and is refracted.
As the angle of incidence continues to increase, what will the angle of refraction eventually do?
Reach 90 degrees
What happens at an angle of incidence of 90 degrees? (in terms of what the refracted ray does and the resulting light)
The refracted ray lies along the boundary between the two media and no light passes into the second medium.
What is the angle of incidence that produces a refracted ray at an angle of 90 degrees from the normal called?
The Critical Angle
Critical Angle Definition
The angle of incidence that produces an angle of refraction of 90 degrees.
What does the size of the critical angle depend on?
The indices of refraction of the two media.
What happens when the angle of incidence is larger than the critical angle? (In terms of angle of refraction size and the reason for it)
The angle of refraction cannot get any larger because the refracted ray would no longer be in the second medium.
So, at angles of incidence that are greater than the critical angle, what happens?
No refraction occurs, and all the light is reflected back into the first medium.
What is the phenomena called when all light is reflected back into the first medium?
Total Internal Reflection
Total Internal Reflection Definition and when does it occur?
The phenomenon in which incident light is not refracted but is entirely reflected back from the boundary; occurs when light travels from a medium in which its speed is lower to a medium in which its speed is higher.
When does total internal reflection only happen?
When light travels from a medium in which its speed is lower to a medium in which its speed is higher.
What happens when the angle of incidence is smaller than the critical angle?
Both refraction and reflection occur at the boundary between the two media.
What happens when the angle of refraction reaches 90 degrees?
The refracted ray lies along the boundary between the two media.
What happens when the angle of incidence is larger than the critical angle?
All the light is reflected back into the first medium.
Two conditions that are necessary for total internal reflection.
- Angle of incidence is greater than the critical angle.
- Light is travelling from a more dense to less dense medium; =lower to higher speed=bends away from the normal=angle of refraction increases past 90 degrees = n1 > n2
How strong are reflection and refraction when the angle of incidence is less than the critical angle?
-Refraction is strong.
-Reflection is weak.
How strong are reflection and refraction when the angle of incidence is the critical angle?
-Refraction is weak.
-Reflection is strong.
Light following a what type of path takes less time than following a straight path when travelling from one medium to another?
A bent path
In a single medium, what is the path that will take the least time?
A straight line
