Modern Physics

photoelectric effect concludes that

light consists of discrete packets of energy called photons

each photon has energy proportional to its

frequency (E=hf)

for the photoelectric effect there is a minimum _____ required to emit _____

frequency, electrons

Compton effect demonstrates that

photons have momentum (p=h/λ). (x ray photon collides with an electron)

matter waves

material particles have a wave-like behavior inversely proportional to their momentum

rutherford gold foil experiment

atom consists of small, positively charged nucleus surrounded by negatively charged electrons

isotopes

same number of protons but a different number of neutrons

for lighter nuclei the ratio of

protons and neutrons is almost one to one

for heavier nuclei the ratio of

protons and neutrons is not one to one. (more neutrons)

binding energy

energy needed to bind the nucleus together and is observed because the actual mass of a nucleus is less that the additive sum of its constituent particles

radioactive decay

name given to the process of unstable isotopes emitting particles and photons

ion

charged atom

ionization energy

amount of energy needed to free an electron from the atom

when will an electron make a transition from a lower energy state to a higher energy state

only when it absorbs a photon equal to a given possible/allowed energy difference

process by which an unstable nucleus decays into a more stable one is

probabalistic

half life

time it takes on average for half of the amount of material present to undergo radioactive decay

if the frequency is too low raising intensity

doesn’t cause any electrons to be emitted, (total energy increases but energy per photon is the same)

work function

minimum amount of energy needed to free an electron

blackbody radiation

emitted radiation by an object solely by virtue of its temperature

Heisenberg uncertainty principle

due to the wave nature of small particles, it is impossible to determine precisely both the simultaneous position and momentum of the particle

The E=mc² equation means that

mass can be changed into energy and vice versa

electrons remain in ___, ____ energy states

discrete, quantized

a perfect black body

absorbs all colors

on a wavelength intensity graph what does the peak indicate

temperature (left is higher temp)

energy state graph for an electron

up (n=1→n=2) means absorbed a photon, can only go up from n=1

down (n=2→n=1) means emitted a photon, can go down from n=#

stopping voltage

even perfectly aligned electrons don’t make it

if two gasses are combined, how does the combined emissions spectrum look

just add the two parts together

an emissions spectrum is mostly

black

an absorption spectrum is mostly

rainbow

A

atomic mass number (# nucleons)

Z

protons

N

neutrons

the bigger the nucleus the

harder it is to keep together, more mass turns into binding energy

alpha decay

shoots out alpha particle (A=4, Z=2)

Original nucleus: A - 4, Z-2

+energy

Beta minus decay

original: Z+1

shoots out electron (A=0,Z=-1)

+energy

Beta plus decay

original: Z-1

shoots out positron (a=0, z=1)

+energy

gamma decay

original goes to a lower/less excited state

emits EM photon