1. Light and Special Relativity

what is the refractive index

a measure of how much the material slows down light passing through it

what is absolute refractive index

the ratio of the speed of light in a vacuum to the speed of light in the medium

what happens when the light ray is smaller than the critical angle

most light is refracted into air and partially reflected

what is the critical angle

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

when does total internal reflection occur

when the angle of incidence is greater than the critical angle

what is n

refractive index

why is a spectrum produced in a prism

different frequencies have different refractive indices

what is interference the evidence of

that light has a wave model

what is constructive interference

when 2 sets of waves meet in phase when both peaks arrive creating a maxima

what is destructive interference

when 2 waves arrive at a point completely out of phase creating a minima

what is the part in between 2 sets of waves called

central maxima

what is the value of m at the central maxima

0

what is the formula for path difference for a maxima

path diff = m x λ

what is the formula for path difference for a minima

path diff = (m+1/2) x λ

what is d in diffraction grating

the separation of the slits

what are differences between spectra from prisms and gratings

prism: 1 spectrum produced, bright images, less widely spread

grating: many spectra produced, less bright images, more spread out

what happens when the bright spots of a laser are closer together on a grating

theres a smaller wavelength as the waves spread out less leading to a smaller angle at which constructive interference occurs

what does a decrease the distance between slits do on a grating

increases the distance between maximas

what does coherent waves mean

the sound waves from have a constant phase relationship with the same frequency, wavelength, and velocity

what are the 2 principles of relativity

when 2 observers are moving at constant speeds relative to one another, they will observe the same laws of physics

the speed of light is the same for all observers

what is t

proper time

what is t’

dilated time thats always longer than the proper time

what is l

proper length

what is l’

contracted length thats always shorter than the proper length

what is irradiance

power per unit area on a surface

what are the units of irradience

W/m2

what is the relationship between irradiance and the distance from a point source

theyre inversely proportional

describe an experiment to prove the inverse square law for a point source

darken a room

measure the distance from a lamp to an irradiance meter

measure the level of irradiance

then do 1/d²

why does irradiance decrease when distance increases

the area of the light increases

the power of the light source remains the same

what is the photoelectric effect evidence of

the particle model of light

how does the photoelectric effect prove the particle model of light

Each photon contains a fixed amount of energy

each photon removes 1 electron

what is threshold frequency

the minimum frequency of a photon required for photoemission

what is the work function of a material

the minimum energy required to release an electron from a surface

what is a photon

a wave particle that carries energy

what happens when an electron has exactly the minimum energy to be released

it releases with no kinetic energy

what happens when an electron has more than the minimum energy to be released

it releases with the extra energy acting as kinetic energy

what is the energy when an electron is at the ground state

its lowest energy

how does an electron move between energy levels

by absorbing or emitting a photon of electromagnetic radiation

what levels have the largest wavelength

the furthest level from the ground state

what levels have the smallest wavelength

the closest to the ground state

what conditions are needed for an electroscope to be discharged

if its negatively charged

the light has equal or more than the threshold frequency

what are features of the bohr atom

electrons can only occupy discrete energy levels

a positively charged nucleus

each line in a spectrum is produced when an electron moves from one energy level to another

what are the 3 types of spectrum

continuous

emission

absorption

what is a continuous spectrum

where theres a complete range of wavelengths

how are emission spectrums produced

if an electron is in an excited state it can return to a lower energy level emitting a photon

different transitions produce different frequencies of photons

how can some lines be brighter than others

more electrons are making transitions to other energy levels per second

there are more photons emitted per second of that specific energy producing brighter lines

what do absorption spectrums look like

full range of wavelengths but some black lines

how are absorption spectrums made

photons of particular frequencies are absorbed in the atmosphere