optics Flashcards
electromagnetic waves
waves that do not need a medium to travel in
how are electromagnetic waves created
by an oscillating electric and magnetic fields
what are all forms of electromagnetic waves characterized by
their range of frequencies and wavelengths
when light changes mediums, what else changes?
its speed and direction
refraction
the idea that the more the difference in speed, the greater the light bends when it changes mediums
illuminance
the intensity of light falling onto a surface. measured in lux
illuminance equation
E=θv / 4 πr^2 (θv is the luminous flux which is given en in lumens)
polarized light
light where the EM wave only vibrates in one direction. Light will be polarized in the direction of the electric field
what happens when unpolarized light passes through a polarizer?
the final intensity of the light will be one half of the initial intensity of the light wave
what direction is a beam of light polarized in?
the direction of the polarizers transmission axis
law of malus
If =Iicos^2θ
l= intensity
reflection
when a wave hits a surface or a boundary and bounces off in a different direction
when will waves be reflected
anytime they encounter a boundary between two mediums
wave front
the surface over which the phase of a wave is constant. given that all particles of the medium are undergoing the same motion
sperical wave front
where waves move outward in three dimensions with rays that point radically outward
plane wave front
where the waves move outward in one direction with the rays pointing in that same direction
what angle will rays be at to wave fronts
right angles
normal line
the line that is perpendicular to the surface is placed so that its located where the ray that enters the mirror travels
incident ray
the ray that hits the mirror then is reflected by the mirror at the location of the normal line
angle of incidence
the angle between the incident ray and the normal
angle of reflection
the angle between the mirror and the reflected ray
law of reflection
when light is reflected off a surface the angle of incidence equals the angle of reflection
specular reflection
when a beam of light is reflected from a smooth surface
diffuse reflection
when a beam of light is reflected off a rough surface
plane mirror
a perfectly flat mirror
what do plane mirrors create
virtual image, same size as the object, the image will be upright, but reversed right to left.
concave mirror
a mirror thats curved in
convex mirror
a mirror that is flexed out, bulges outwards like the surface of a ball
center of curvature of a spherical mirror
center of the spherical shell with a radius of R of which the curved mirror is a section of
principle axis
a straight line drawn through the center of curvature and the midpoint of the mirror. the center of curvature lies on this line and it intersects the mirror at right angles
where will the rays converge on a concave mirror?
infront of the mirror
focal point
where the rays of a mirror reflect and converge
focal length
distance between the surface of the mirror to the focal point
the equation for focal length of a CONCAVE mirror
f= 1/2 R
where will rays of light that are parallel to the principle axis always reflect on a concave mirror
through the focal point
which way do rays spread on a convex mirror
outwards
does light pass through the focal point on a convex mirror?
no
incoming rays of light that are parallel to the principal axis of a convex mirror are…
spread out
equation for focal length on a CONVEX mirror
f= - 1/2R
the focal length of a mirror will be positive if…
the focal point is in front of the mirror
CONCAVE mirror always have a ___ focal length
positive
the focal length will always be negative if
the focal point is behind the mirror
CONVEX mirrors will always have a ___ focal length
negative
mirror equation
1/do + 1/di = 1/f
when will the image distance be positive
if its infront of a mirror
when will the image distance be negative
if the image is behind the mirror
what does a positive image distance tell you
its a real image
what does a negative image distance tell you
its a virutal image
magnification equation
m= hi/ho = -di/do
if the magnification is positive the image is…
upright
if the magnification is negative the image is…
inverted
if the magnification is less than 1 the image is
reduced
if the magnification is greater than 1 the image is
magnified
the speed of light through any material is ___ than its speed in a vacuum
slower
snells law
relates the indices of refraction of the two mediums
to the directions of propagation in terms of the angles to the normal line.
snells law equation:
n1sinθ1=n2sinθ2 —–> θ1 is known as the angle of incidence, while θ2 is known as the angle of refraction
light will be bent towards the normal when…
it slows down because it has entered a material with a higher index of refraction
light will be bent away from the normal when…
it speeds up because it has entered a material with a lower index of refraction.
the greater the change in the index of refraction…
the greater the change in the direction of the light.
If a ray of light goes from one material to another along the normal
it does not change direction
Total Internal Reflection
the reflection of the total amount of incident light at the boundary between two media
when does total internal reflection happen
when a ray of light in a medium of higher index of refraction approaches the other medium that has a lower index of refraction, at an angle of incidence greater than the critical angle
As the angle the angle of incidence for the ray of light increases inside of a denser medium….
the angle of refraction also
increases outside of the medium.
When the angle of incidence is such at the angle of refraction is 90o, then the refracted beam will be …
parallel to the surface of the thicker medium
in total internal reflection the angle of incidence is known as the
critical angle
when does total internal reflection happen (angle wise)
when the angle of incidence is larger than the critical angle
critical angle equation
θc=sin−1(n2/n1)
A material has a higher index of
refraction for light towards…
the blue end of the visible spectrum
dispersion
the spreading out of refracted light according to color
converging lenses
lenses that are thicker in the middle than the outer edge
Converging lenses take parallel rays of light and…
bring them together at a position known as the focal point
diverging lenses
lenses that are thinner in the middle than the outer edge
Diverging lenses take parallel rays of light and…
spread them out as if they’re diverging from the focal point
double convex lens
a lens that bulges out in the middle. It is a converging lens where all the parallel rays that are incident on it focus down to a focal point.
double concave lens
lens is one that curves inward like a cave. a diverging lens where all the parallel rays that are incident on it are bent away from the axis of the lens in such a way they can be extended back to appear as if originating from a focal point
optical power
the reciprocal of the focal length. measured in diopter (D)
midpoint ray
travels directly through the center of a lens without changing direction. The midpoint ray holds for both converging and diverging lenses
parallel ray
travels parallel to the primary axis.
- When it passes through a convex lens it will pass through the focal point of the lens on the other side
focal point ray
For a convex lens the ray will travel through the focal point of
the lens and emerge parallel to the primary axis on the other side.
For a concave lens the ray will enter the lens in such a way that
the incident ray can be extended through the focal point on the other side. The refracted ray will be refracted so that it travels parallel to the primary axis.
thin lens equation
1/do + 1/di = 1/f
the focal length will be ___ for convex/converging lenses
positive
the focal length will be ___ for concave/diverging lenses
negative
the image distance will the ___ for images on the opposite side of the lens from the object
positive = real image
the image distance will be ____ for images on the same side of the lens as the object
negative = virtual image
the magnification will be ___ for upright images for lenses
positive
the magnification will be ___ for inverted images for lenses
negative
interference
caused by the superposition of waves. where the displacement of two or more waves is the sum of the displacements of the individual waves.
constructive interference in light waves results in
increase in brightness
destructive interference in light waves results in
decrease in brightness
coherent light sources maintain…
a constant phase relative to one another which means all the waves look the same
incoherent light sources have…
differences that vary randomly with time. you cant see the light interference clearly with an incoherent light source
monochromatic light
a light of a single color or frequency
laser
a device that emits light that is both monochromatic and coherent
if a wave is in phase of a full wavelength out of phase what occurs
constructive interference
if a wave is half a wavelength out of phase what occurs
destructive interference
path length in wave equation for constructive interference
L1 − L2 = m λ where m = 0, 1, 2, 3, …
path length in wave equation for destructive interference
L1 − L2 = (m + 1/2 )λ where m = 0, 1, 2, 3…
Two slit experiment/ youngs double slit experiment
First preformed in 1801 by Thomas Young, his experiment consisted of a monochromatic coherent light that illuminates two slits which then shines on a distant screen
what resulted from youngs double slit experiment
an interference pattern as you
can clearly see constructive and destructive interference occurring with bright and dark spots occurring
Huygen’s Principle
states that every point on a wave front acts like a point source for new waves
A bright fringe will occur wherever…
the path length difference is equal to an integer number of wavelengths.
the distance between slits equation for bright fringes
In equation form: d sin θ = m λ where m = 0, 1,
2, 3…
the distance between slits equation for dark fringes
d sin θ = (m + 1/2 )λ where m = 0, 1, 2, 3, 4…
location of the interference fringes equation
y=Ltanθ
diffraction
The bending of a wave around a barrier or through an opening
what happens to light when is passes through a single slit
it diffracts
diffraction pattern
the interference of these new waves with one another that generates a series of bright and dark fringes
width between slits for dark fringes equation
Wsinθ =mλ where m=±1,±2,±3….
small angle approximation
sinθ ≈ tanθ ≈ θrad (only true for angles less than 15 degrees)
SAA 2nd equation
Wy/L = m λ
If we have a circular opening of diameter D, we can see it will produce a dark fringe an an angle given by
sinθ=1.22λ/D
diffraction grating
a screen with large number of slits. multiple slits diffract light like a prism
principal maxima
a series of very sharp widely spaced bright fringes on an interference pattern
secondary maxima
a series of relatively dark regions that are weaker on an interference pattern
what does the angle at which a principal maxima occurs at depend on
the wavelength of the light
distance between slit equation for constructive interference
d sin θ = m λ where m = 0, 1, 2, 3, 4…
A grating with a smaller spacing between slits will spread light out over a…
wider range of angles than one with a larger spacing between slits
Diffraction gratings work for both…
the transmission of light and the reflection of light.
a convex mirror will create an image that is…
upright, reduced, virtual
a concave mirror will create an image that is what when the object distance is greater than the focal length
inverted, enlarged, real
a concave mirror will create an image that is what when the object distance is less than the focal length
virtual and upright
