Light and Optics Flashcards
radio waves
on one end of the electromagnetic spectrum; long wavelengths, low frequency, and low energy
gamma rays
on one end of the electromagnetic spectrum; short wavelength, high frequency, and high energy
order of waves from lowest to highest energy
radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and then gamma waves
visible spectrum
400 nm (violet) to 700 nm (red)
electromagnetic waves
are transverse waves that consist of an oscillating electric field and an oscillating magnetic field; these two fields are perpendicular to each other and the direction of propagation of the wave
units for wavelengths
Angstrom (A)= 10^-10 m
speed of electromagnetic waves in a vacuum
speed of light; 3.00x10^8 m/s
c=f(lambda)
(for the test, this is how fast it moves in air)
blackbody
refers to an ideal absorber of all wavelengths of light
rectilinear propagation
light traveling in a homogeneous medium will travel in a straight line
reflection
the rebounding of incident light waves at the boundary of a medium
law of reflection
states that an incident angle will equal the angle of reflection, as measured from the normal
theta1 = theta2
both are measured from the normal
normal
a line drawn perpendicular to the boundary of a medium; all angles in optics are measured from the normal, not the surface of the medium
real images created from a mirror
when the light actually converges at the position of the image; will have a positive distance (i>0)
virtual image created from a mirror
when the light only appears to be coming from the position of the image but does not actually converge there; ex: looking into a mirror, the reflected light is in front of the mirror but the image appears to be behind it; will have a negative distance (i<0)
plane mirrors
flat reflective surfaces, causes neither convergence nor divergence of reflected light rays; always create virtual, upright images and the image is always the same size as the object; r=f=infinity
spherical mirrors
have centers and radii of curvature as well as focal points; are either concave or convex
center of curvature
a point on the optical axis located at a distance equal to the radius of curvature from the vertex of the mirror; it would be the center of the spherically shaped mirror if it were a complete sphere instead of just a piece
concave mirrors
converging systems and can produce real, inverted images or virtual, upright images, depending on the placement of the object relative to the focal point; the center and radius of curvature are in front of the mirror
convex mirrors
diverging systems and will only produce virtual, upright images; the center and radius of curvature are behind the mirror
focal length (f)
f=r/2
it is the distance between the focal point and the mirror
and r is the distance between the center and the mirror-radius
optics equation
1/f= 1/o + 1/i =2/r
often used to calculate the image distance
optics equation for plane mirrors
1/o + 1/i = 0 or i=-o
magnification (m)
a dimensionless value that is the ratio of the image distance to the object distance: m=-i/o
negative magnification
signifies an inverted image
positive magnification
signifies an upright image
|m|<1
image is smaller than the object
|m|>1
image is larger than the image
|m|=1
the image is the same size as the object
ray diagram rules for concave mirrors
- ray that strikes the mirror parallel to the axis is reflected back through the focal point
- a ray that passes through the focal point before reaching the mirror is reflected back parallel to the axis
- a ray that strikes the mirror at the point of intersection with the axis is reflected back with the same angle measured from the normal
what happens to the image if the object is placed at the focal point?
there is no image, the image will be at infinity (i=infinity)
ray diagram rules for convex mirrors
the further away the object, the smaller the image is
refraction
the bending of light as it passes from one medium to another and changes speed
index of refraction (n)
n=c/v
c=speed of light in a vacuum
v=speed of light in the medium
n=the index of refraction of the medium, dimensionless
Snell’s law
n1 sin(theta1)=n2 sin(theta2)
theta is in respect to the normal
how is light bent when the light enters a medium with a higher index of refraction?
n2>n1
the light is bent toward the normal
how is light bent when the light enters a medium with a lower index of refraction?
n2
critical angel (theta c)
the refracted angle (theta2) equals 90 degrees; at this point the refracted light ray passes along the interface between the two media
theta c= sin-1(n2/n1)
total internal reflection
phenomenon in which all the light incident on a boundary is reflected back into the original material; results with any angle of incidence greater than the critical angle
lenses
refract light to form images of objects
thin symmetrical lenses
have focal points on each side, and the focal length is the same for both
convex lenses
are converging systems and can produce real, inverted images or virtual, upright images
concave lenses
are diverging systems and will only produce virtual, upright images
Lensmaker’s equation
used for lenses where thickness is not neglected, the focal length is related to the curvature of the lens surfaces and the index of refraction of the lens
1/f = (n-1) [(1/r1)-(1/r2)]
n=index of refraction
r1= radius of curvature of the first lens surface
r2= radius of curvature of the second lens surface
ray diagram rules for lens
- ray parallel to axis -> refracts through the focal point of front face of the lens
- ray through or toward focal point -> refracts parallel to the axis
- ray to center of lens -> continues straight through with no refraction
power (P) of lenses
P=1/f
f=focal length
positive for converging lens and negative for diverging lens and it is measured in diopters
hyperopia
farsightedness; people can see distant objects clearly and need converging lenses
myopia
nearsightedness; people can see near objects clearly and need diverging lenses
focal length of multiple lens system
1/f = 1/f1 + 1/f2 + 1/f3 + ……
power of multiple lens system
P= P1+P2+P3+……
magnification of multiple lens system
m= m1xm2xm3x……
aberrations
errors
spherical aberration
a 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 the lens; creates an area of multiple images with very slightly different image distances at the edge of the image
dispersion
when various wavelengths of light separate from each other; ex: splitting of white light into its component colors using a prism
chromatic aberration
a dispersive effect within a spherical lens; can result in rainbow halo around images depending on the thickness and curvature of the lens
diffraction
the bending and spreading out of light waves as they pass through a narrow slit or around an obstacle
single slit diffraction
light that goes through a narrow slit, on the order of the light wavelength, the light waves seem to spread out (diffract); as the slit is narrowed, the light spreads out more
positions of dark fringes in slit-lens setup
(a)sin(theta) =n(lambda)
a= width of the slit theta= angle between the line drawn from the center of the lens to the dark fringe and the axis of the lens n= integer indicating the number of the fringe lambda= wavelength of the incident wave
interference
when interacting waves result in the addition of the displacements of waves
constructive interference of multiple slits
when the two lights waves resulting from the double slit show constructive interference and end up as bright fringes (maxima) on the plate behind it
destructive interference of multiple slits
when the two lights waves resulting from the double slit show destructive interference and end up as dark fringes (minima) on the plate behind it
position of dark fringes in double-slit setup
d sin(theta)= (n+0.5) (lambda)
d=distance between two slits
theta= angle between the line drawn from the midpoint between the two slits to the dark fringe and the normal
n=integer indicating the number of the fringe
lambda= wavelength of incident wave
Young’s double slit experiment
shows the constructive and destructive interference of waves that occur as light passes through parallel slits, resulting in minima (dark) and maxima (bright) of intensity
plane polarized light
light in which the electric fields of all the waves are oriented in the same direction (their electric filed vectors are parallel)
polarizers
allow only light with an electric field pointing in a particular direction to pass through; they only let through the portion of the light parallel to the axis of the polarizer
circular polarized light
created by exposing un-polarized light to special pigments of filters; has a uniform amplitude but continuously changing direction resulting in a helical orientation
