Ch. 8: Light and Optics Flashcards
electromagnetic waves
electric field and magnetic field vectors that oscillate perpendicular to each other and propagate as transverse waves
electromagnetic spectrum from low frequency/high wavelength to high frequency/low wavelength
radio –> AM –> FM –> Microwaves –> IR –> visible light –> UV –> x-rays –> gamma rays
speed of light
speed at which all electromagnetic waves travel in a vacuum
c = 3.00 E8 m/s
equation for the speed of light
c = frequency * wavelength
wavelengths of the visible spectrum
400nm (violet) - 700nm (red)
rectilinear propagation
when light travels in a straight line through a homogenous medium
reflection
rebounding of incident light waves at the boundary of a medium
bounce of second medium, travel back through first medium
law of reflection
theta 1 = theta 2
where theta 1 is the incident angle, theta 2 is the reflected angle and the normal is drawn perpendicular to the boundary medium
real image
light converges at the position of the image created by a mirror
Has POSITIVE image distance, in front of the mirror
can be projected onto a screen
virtual image
light appears to, but DOES NOT actually, converge at the position of the image created by mirror
Has NEGATIVE image distance, behind the mirror
CANNOT be projected onto a screen
plane mirror surface image
flat and reflective surface
always create VIRTUAL images because light remains in parallel and does not converge or diverge
image always appears equal distance behind the mirror as object is in front of it
spherical mirrors
concave or convex with
center of curvature
where the center of a spherical mirror would be if it were a complete sphere
radius of curvature
what the radius of a spherical mirror would be if it were a complete sphere
converging mirrors
concave mirrors
cause parallel incident rays to converge after reflection, causing a larger and closer image
diverging mirrors
convex mirrors
cause parallel incident rays to diverge after reflection, causing smaller and further images
focal length (f)
distance between mirror and focal point (F)
focal length for all spherical mirrors
f = r/2
object distance (o)
distance between object and mirror
image distance (i)
distance between image and mirror
Positive = real image, in front of the mirror Negative = virtual image, behind the mirror
equation relating focal length, object distance, and image distance
1/f = 1/o + 1/i
= 2/r for spherical
= 0 for plane
focal length for all plane mirrors
f = infinity
equation for magnification (m)
m = - i / o
negative = inverted image positive = upright image
where does a ray parallel to the axis reflect
thought the focal point
where does a ray through the focal point reflect
parallel to the axis
where does a ray at the center of the mirror reflect
at same angle relative to normal
refraction
bending of light as it passes from one medium into another and changes its speed
equation for index of refraction
n = c/v
refraction index = speed of light / speed in particular medium
snell’s law for light that passes from one medium to another
n1 sin theta 1 = n2 sin theta 2
where does light bend as it enters a medium with a higher refractive index
n2 > n1…therefore…sin theta 1 > sin theta 2…bends towards normal
where does light bend as it enters a medium with a lower refractive index
n1 > n2…therefore…sin theta 2 > sin theta 1…bends away from the normal
critical angle
refracted angle theta 2 = 90 degrees
refracted angle passes along interface between the two media
total internal reflection
occurs when angle of incidence is greater than the critical angle, and refracted light is reflected back into the original medium
converging lenses
- thicker at center
diverging lenses
- thin at center
where does a ray parallel to the axis refract
through the focal point to the front face of the lens
where does a ray through or toward the focal point before reaching the lens refract
refracts parallel to the axis
where does a ray to the center of the lens refract
continues straight with no refraction
lensmaker’s equation
thickness is not negligible
1/f = (n - 1)( 1/r1 - 1/r2 )
where r1 is the radius of the first lens surface and r2 is the radius of the second lens surface
which kinds of mirrors and lenses are similar and have similar properties
concave mirrors and convex lenses = converging
convex mirrors and concave lenses = diverging
equation for power of a lens
P = 1/f
unit of power is diopters
equation for equivalent focal length
1/f = 1/f1 + 1/f2 + 1/f3…
equation for equivalent power
1/P = 1/P1 + 1/P2 + 1/P3…
spherical aberration
blurring of the periphery of an image as a result of inadequate reflection of parallel beams at the edge of a mirror or inadequate refraction of parallel beams at the edge of a lens
dispersion
when various wavelengths of light separate from each other
chromatic aberration
dispersive effect within a spherical lens
white light is split, causing rainbow images
diffraction
the splitting out of light as it passes through a narrow opening or around an obstacle
fringe pattern of single slit diffraction with lens
central bright fringe (zeroth) twice as wide as fringes on either side
location of dark fringes is
a * sin theta = n * wavelength
what do bright fringes (maxima) represent
where light waves experience constructive interference
what do dark fringes (minima) represent
where light waves experience destructive interference
fringe patter of double slit diffraction with lens
central bright fringe (zeroth) equal wide as fringes on either side
location of dark fringes is d sin theta = (n + 0.5) * wavelength
diffraction gratings
multiple slits arranged in patterns that creates prism-like patterns as different wavelengths interact
thin film interference, CDs…
plane-polarized light
light with all electric field vectors parallel
circular polarized light
light with uniform amplitude and continuously changing direction, causing helical orientation in the propagating waves
