Laws of Reflection and Refraction Lecture 2 Flashcards
Light striking an interface between two media, and entering the new medium changes what?
Velocity, and a change in direction in most cases.
During transparency, light part of the light is ________, most ________ and some of the material is ___________.
Reflected; refracted; absorbed.
There are two types of reflection. What are they? Which so we care about more?
Specular and diffuse. Consider specular reflection in geometrical optics.
The angle of incidence is equal to the angle of reflection is known as what law?
Law of Reflection.
Light which is reflected leaves the surface traveling in what direction?
Opposite.
What is Fresnel’s Law of Reflection?
R=(n’-n/n’+n)^2 x 100
n=refractive index of objects space (left of interface)
n’=refractive index of image space (right of interface).
What does Fresnel’s Law of Reflection describe?
Amount of light reflected from otherwise transparent and refractive interface (not for mirrors) in percentage.
What is the index of refraction of a medium?
n=c/v
c=speed of light in a vacuum (3 X 10^8 m/s)
v=speed of light of a different medium.
The more denser the medium, the _____ the speed of light for that medium, the ______ the refractive index for that medium.
Lower; higher.
For any optic problem without a specified refractive index, what value do you use?
1.50.
In reality though, the refractive index (n) depends on what two things?
Frequency and wavelength.
Since f is constant, the refractive index depends upon the wavelength of light used. What wavelength i sued as a reference wavelength?
589.30 nm.
True or False: Refractive index is wavelength independent.
False. Dependent.
The Law of Refraction is also known as what?
Snellen’s Law.
What is the Law of Refraction?
Says refraction occurs when light passes from one medium into another medium.
What is the formula of Snellen’s Law?
The index of the medium before refraction times the sine of incident angle is equal to the index of the medium after refraction times the sine of refracted angle.
n X sin 0 =n’ X sin 0’.
When going from a less dense into a more dense material, angle of incidence is _________ then the angle of refraction.
Greater.
When going from a more dense into a less dense material, angle of incidence is _________ then the angle of refraction.
Less.
The largest possible angle for 0 or 0’ is what?
90 degrees.
Going from a more dense into a less dense material, when the angle of incidence exceeds a critical angle (say 70 degrees), all the light is reflected internally. What is this called what?
Total Internal Reflection.
When angle of refraction is larger than the angle of incidence
True or False: Total internal reflection occurs when light is in a more dense medium and wants to go into a less dense medium,.
True.
What practical application in Optometry is there that some what proves the total internal reflection theory?
Sclerotic scatter.
Why do we see mirages?
Happens only on hot days because cements becomes a lower refractive index than the sky so total internal reflection occurs due to high medium to low medium light refraction.
