Lect. 8 Light & Optics Flashcards
transverse wave
travelling oscillation of an electric and magnetic field (perpendicular to each other)
direction of propogation is perpendicular to both fields
electromagnetic wave
constant value for each particular wave
= E / B
speed of an electromagnetic wave (c) through a vacuum
a small sliver from the electromagnetic spectrum
includes wavelengths 390 - 700 (*10^-9 nm)
light
“color” / wave in electromagnetic spectrum w/ the highest energy, shortest wavelength, and highest frequency
travels slowest through a medium (700)
violet light
“color” / wave in electromagnetic spectrum w/ the lowest energy, longest wavelength, lowest frequency, travels fastst through a medium (390 nm)
red light
“beyond violet”
just beyond the visible spectrum on the smaller wavelength side; very high in energy
Ultraviolet Light
just beyond visible spectrum on the longer wavelength side; very low in energy
Infrared light
Equation: speed of light (wavelength w/ corresponding frequency)
c = f * wavelength
used to find the speed of light constant through some medium
compares c in a vacuum to c through some medium
Index of Refraction (n)
Equation: index of refraction (n)
n = c / v
All media have an index of refraction (n) ____ than 1.
greater than
A higher index of refraction (n) indicates that a wave moves _______ through the medium
slowly
Index of refraction for water
n (water) = 1.3
Index of refraction for glass
n (glass) = 1.5
light w/ electric fields all oriented in the same direction
plane-polarized light
The dual nature of light states that light acts like a ____ and a _____.
wave and a particle
angle at which a light ray strikes an interface
angle of incidence
angle at which light ray is reflected off an interface
angle of reflection
angle at which a light ray may refract off an interface
ange of incidence = angle of reflection
angle of refraction
Equation: Snell’s Law
-Described angle of Refraction
n1 * sin(ø)1 = n2 * sin(ø)2
Note: n1 and n2 = respective interfacing media; doesn’t matter which is which
When light crosses into a new medium, _____ is constant but ____ changes.
frequency is constant but wavelength changes
If the index of refraction (n) goes up, light slows down and ______ shortens
wavelength
If the index of refraction (n) goes down, light ______ and wavelength lengthens
speeds up
Equation: Energy of a Photon
E = h * f
Note: h = Planck’s constant
If the frequency is doubled in the energy for a single photon, you also double the number of photons and increase intensity by _____
4
if the angle of incidence is large enough, all photons reflect and none refract;
total internal reflection
Note: angle is called the CRITICAL ANGLE
white light is split into FREQUENCIES of the visible spectrum by a prism
chromatic dispersion
bending waves around a corner through a small opening
diffraction
when diffracting light, a smaller hole _____ spreading of the light
increases
diffraction can create light/dark bands or colors by ____ when waves meet
interference
interference that results in bright bands
constructive interference
interference that results in dark bands
destructive interference
Mirrors _____ light
reflect
lenses _____ light
refract
an image that does not actually exist except to the observer; no light rays come from this image;
Ex: reflection in a flat mirror; mirage, fish seen from shore
virtual image
an image that exists separately from the observer; rays of light intersect and emanate from the point of intersection
real image
mirror that is curved out to the observer
convex mirror
mirror that is curved in, away from the observer
concave mirror
lens that acts like a concave mirror
converging lens
lens that acts like a convex mirror
diverging lens
if the center of a lens is thicker than its ends, it will _____ light regardless of the shape or which direction light moves through the lens
converge
thiCker Center Converges
If the center of a lens is thinner than its ends, it will _____ light
diverge
small section of a curve that could be extended to form a perfect circle; radius of a small section is = to the radius of the entire circle
smaller value means a sharper curve
radius of curvature
type of mirror (ex: convex / concave)
only parabolically curved surfaces will focus all parallel lines to a single focal point; all equations require rays of light at small angles
spherical mirrors
light from horizontal rays is reflected by concave mirrors or refracted by converging lenses to focus on a single point
Affected by: refractive index of lens, medium lens is in, and radius of curvature
focal point
Convex mirrors and diverging lenses reflect/refract horizontal rays ________, found by tracing back along the reflected or refracted ray behind the mirror/lens
outward from a single point
focal point for any mirror or lens is separated from the mirror or lens by the ____
focal length
Equation: focal length of mirror related to radium of curvature
f(mirror) = 1/2 * r
quality of a lens that is inverse of focal length
measured in diopters
SI unit = 1 / m
Power
ratio of the size of the image to the size of the object
can compare height of the image to the heigh of the object
= negative ratio of distance of the image over the distance of the object from the light source
lateral magnification (m)
Equation: Lateral Magnification
m = - d(i) / d(o) = h(i) / h(o)
the closest distance an object can be to an individual while they can still focus clearly on the object
near point
angle occupied by an object when at the near point compared to the angle occupied by the image of the object when in front of a lens
angular magnification: m(q)
Equation: Angular magnification
m(ø) = ø(image) / ø(np)
Equation: Thin Lens Equation
1/f = 1 / d(o) + 1 / d(i)
Note: f = focal length
Applicable to any mirror or lens
Mirror that makes a positive, real, inverted image
unless object is w/i the focal distance!
concave mirror
mirror that always makes a negative, virtual, upright image
convex mirror
type of lens that makes a positive, real, inverted image
unless object is w/i the focal distance!
converging lens
type of lens that always makes a negative, virtual, upright image
diverging lens
for a _____ mirror and a _____ lens, focal length is always negative
convex mirror
diverging lens
for a ______ mirror and a ____ lens, focal length is always positive
concave mirror
converging lens
