MCAT Physics: Light and Quantum Mechanics

light is what kind of wave

transverse wave composed of oscillating electric and magnetic fields which propgates WITHOUT A MEDIUM

transverse wave

A wave that moves the medium in a direction perpendicular to the direction in which the wave travels

speed of light

c = 3.00 x 10^8 m/s

intensity of light is proportional to

The square of the wave amplitude (strength of the electric field)

when light encounters the interface between two media

light will reflect and refract

reflection equation

angle of incidence = angle of reflection

in reference to the surface normal

refraction definition

bending of light as it is transmitted from one medium to another

index of refraction

how much slower light travels through a medium than through a vaccuum

index of refraction equation

n = c / v

c: speed of light in a vacuum

v: speed of light in the medium

index of refraction of air

1

snells law

n1sinθ1 = n2sinθ2

when light is transmitting to a medium of lower refractive index

θ2 will increase, bending away from the surface normal

when light is transmitted to medium of higher refractive idex

θ2 will decrease, bending towards the surface normal

critical angle definition

the angle of incidence that produces an angle of refraction of 90 degrees

critical angle equation

sin(c) = ( n2 / n1 )

total internal reflection

any incidence angle greater than the critical angle will have the light completely reflected and NOT refracted

diffraction

the spreading out of waves when they encounter an obstacle or aperture about the same size as their wavelength; instead of continuing along a linear path, they spread out as though emerging from a new point source

dispersion

Higher frequencies generally have slightly higher indexes of refraction (bend more) than lower frequencies, allowing prisms to split up white light into its component colors

polarization

occurs when one direction of oscillation is privileged, whether by reflection or transmission through a special material or filter. Only transverse waves can be polarized

plane polarization

removal of all electric field oscillations except from those along one plane parallel to the direction of propagation

circular polarization

Two perpendicular electric field components oscillate 90 degrees out of phase with each other --> superposition of these components creates a field that rotates in a plane perpendicular to the direction of propagation

optics equation

1/f = 1/o + 1/i

f: focal length

o: object distance from mirror

i: distnace from lens that an image is formed

focal length

intrinsic property of lens/mirror; equal to half of the radius of curvature

When is the focal length positive

converging optics: a concave mirror or convex lens

when is focal length negative

diverging optics: convex mirror, concave optic

when is image distance positive

where the image is formed, where the light actually travels: behind a lens and in front of a mirror

magnification equation

m = -i/o

magnification definition

the size of the image compared to the object

real image

Light rays converge, and the image is formed where the light is supposed to go (positive image distance).

positive magnification

upright and virtual image

negative magnification

inverted real image

virtual image

Seems like the light rays converge to an observer, even though they do not actually (negative image distance)

myopia

Nearsighted, the focal length of the eye lens system is too short (light converges before the retina). Needs a diverging lens to form an image at the retina

lens power

P = 1/f

hyperopia

farsightedness, the focal length of the eye's lens system is too long (light doesn't converge), and needs a converging lens to correct.

photoelectric effect

The emission of electrons from a metal when light shines on the metal

energy of a photon

E = hf = hc/λ

energy of a photoelectron

KEmax = hf - phi

phi is the work function

work function

binding energy of the metal target

brightness of the light is proportional to

the number of photons

stopping potential

The minimum potential difference required to stop the highest kinetic energy electrons from leaving the metal plate (no current) in the photoelectric effect.

stopping potential equation

-eVstop = KE(max)

Heisenberg Uncertainty Principle

∆x∆p≥h/2π