Light Flashcards
snells law
n1sinθ1 = n2sinθ2
n is the index of refraction which is dependent upon medium
Ratio of n1 to n2 is =
sinθ2/sinθ1
*Helpful in predicting the direction of refraction when manipulating the medium type
Calculating index of refraction (n)
n = c/v
speed of light in vacuum (3.0 x 10^8) / speed of light in certain medium
True or false:
The index of refraction affects the speed of light traveling through the medium.
True. Speed of light in a medium (v) is inversely proportional to index of refraction of that medium.
True or false:
For smooth surfaces such as a mirror, the angle of reflection is equal to the angle of incidence.
True; θi = θr
Define refraction
The bending of light that takes place as light travels at an angle passing from 1 medium to the next
Total internal reflection
Occurs when light leaving a medium w/ a higher refractive index enters a medium w/ lower refractive index. AND when
θincidence = θreflection
θincendence > θcritical angle
If the refractive indexes of two mediums are equal, is light refracted?
No, light isn’t refracted.
Comparing reflected angle vs. refracted angle on diagram
What is the θrefraction if θincidence = θcritical?
θrefraction is 90˚
This is the max refraction you can have.
Basically when the refractive angle is exactly 90, the incidence angle becomes the critical angle (the angle at which you get the max refraction).
EQUATION for frequency
f = c/λ
Equation for energy of light
E = hf
h is Planck’s constant
Relationship between speed of light and refractive index of medium
Higher refractive index –> slower speed of light
When light travels from a medium w/ higher “n” to a medium with lower “n”, light bends (away/towards) the normal.
away
When light travels from a medium w/ lower “n” to a medium with higher “n”, light bends (away/towards) the normal.
towards
General pattern for refraction comparing n and θ.
If n1 > n2, then θ2 > θ1
and viceversa
Electromagnetic radiation (light) is a (transverse/longitudinal) wave.
Transverse
Electromagnetic spectrum
For a sound wave intensity is directly proportional to amplitude ^2 and energy of the wave.
For light, intensity is directly proportional to what?
The total energy of light emitted and the number of photons emitted from the surface per unit time (causing a more bright spot).
INTENSITY IS NOT RELATED TO THE FREQUENCY OF EACH PHOTON.
Real image vs. virtual image
Real - i is positive; image is in front of the mirror
Virtual - i is negative; image is behind the mirror
If light is completely reflected, incident angle > critical angle; does light travel through only 1 medium or two mediums during total reflection?
Only 1 medium because the light is reflected onto the same medium it came from.
What is the critical angle?
It is the incident angle when the refracted angle = 90˚.
Question: What is the index of refraction of an unknown medium?
Compare the structures of a convex lens vs. concave lens
Convex - center of lens is thicker than edges
Concave - edges thicker than center
How does light pass through a convex lens?
Parallel rays of light passing through lens are bent towards each other into a single focal pt. behind the lens
How does light pass through a concave lens?
Parallel rays of light passing through the lens are bent away from each other
A convex lens is a (converging/diverging) lens.
A concave lens is a (converging/diverging) lens.
converging, diverging
Calculating focal length (f) for MIRRORS ONLY.
f = radius/2
A concave lens always forms a (virtual/real) and (upright/inverted) image.
virtual, upright
Equation calculating different variables: o, i
1/f = 1/o + 1/i = 2/r
o is distance between object & mirror
i is distance between image & mirror
A convex lens forms a (virtual/real) image when the distance of the object from the lens is greater than the focal length.
real
Calculating lens strength (S)
Can use either of 2 equations:
S = 1/f
S = 1/o + 1/i
UNITS: m^-1 or D (diopters)
Calculating magnification (m)
m = -(i/o)
m > 1, enlarged(taller) image
m < 1, smaller(shorter) image
m = 1, same height
Remember when using any equation for a diverging lens, focal length “f” & “i” is (positive/negative).
negative
How can you tell if an image is inverted or upright?
If m is negative, image is inverted.
If m is positive, image is upright.
How can you tell if an image is real or virtual for a mirror? Does this apply to lenses as well?
IF image is in front of the mirror, it is real.
IF image is behind the mirror, it is virtual.
No, for lenses the opposite pattern is observed.
For a thin lens, the image must be ________ if it is on the same side as the object.
a. real
b. virtual
b. virtual
A converging mirror/lens, always has a (positive/negative) focal length.
positive focal length
For a convex mirror, objects are focused (in front/behind) the mirror
behind
Convex mirrors always form (upright/inverted) and (virtual/real) images.
upright, virtual
Concave mirrors form _________ images when the object is located inside the focal length.
upright, virtual
Concave mirrors form _________ images when the object is located outside the focal length.
Inverted, real
Myopia is corrected with what lens type?
Diverging lens - which creates virtual and upright images on same side of object
How does a linear polarization filter work?
ONLY allows in waves parallel to axis of polarization. Blocks electromagnetic radiation with electric fields oriented perpendicular to the axis of polarization, causing them to be absorbed.
How does intensity of a lightbulb change when passed through a polarization filter?
It decreases in intensity by 1/2 because electromagnetic radiation oriented perpendicular does NOT enter the filter.
If a light is polarized, this means the electric field is traveling ________.
In one direction only; either vertical, horizontal OR diagonal
Circular polarized light
What are plane mirrors?
-Reflected light rays from the mirror remain parallel; don’t converge/diverge
-Equidistant image, the distance object is from the mirror is the same distance image is from the mirror
-Image is always VIRTUAL, upright, image height equal to object height
Define dispersion
When various wavelengths of light separate from each other due to having different angles of refraction through the same medium
True or false:
As light enters a medium with a different index of refraction, the wavelength and frequency changes.
False, only the wavelength changes. The frequency stays the same.
Chromic aberration
Splitting of white light through a spherical lens (dispersion) resulting in a rainbow halo around images that causes image blurriness
Spherical aberration
Blurring of the periphery of an image as a result of inadequate reflection/refraction of parallel beams at the edge of a mirror/lens
**When calculating lens strength or any lens equations, make sure units are in METERS
Hyperopia is corrected with what type of lens?
Converging lens producing a real and inverted image.
Hyperopia causes objects to focus (in front/behind) the retina.
behind
*behind and hyperopia both have H’s
Myopia can be caused by an eyeball that is too (long/short) or too (much/little) focusing power.
long, too much focusing power
Myopia is fixed by a ________ lens.
Diverging
Thin-film interference
The production of multiple colors of light generated by reflection events that occur within a system composed of 2 layers of semitransparent media. Different interference patterns of the waves at different surfaces are caused by variable thicknesses of the two mediums.
As you move an object closer to your eye, how does your lens accommodate?
The lens gets more curved, to decrease its focal length and increase its refractive power.
Focal length and refractive power are (directly/inversely) proportional.
Inversely:
Power or lens strength = 1/f
Define near point and far point
Near point - the closest distance of an object you can see
Far point - the furthest distance you can see, usually its infinity with perfect vision
Multiple lens systems
Add the refractive powers for multiple lenses together.
Multiply the magnifications for multiple lens.
M = m1m2m3
How does thin film interference occur?
It occurs when light enters a semitransparent medium, some of it which is reflected from the top and some of it travels down to be reflected from the bottom surface (since the fluid is somewhat transparent). The reflected light rays from the bottom surface interfere with the reflected light rays at the top of the surface creating multiple wavelengths (multiple colors of light).
Does a near or far-sighted person have a more powerful lens?
Near sighted person, more powerful lens & decreased focal point
