03/19 EM spectra Flashcards
what is the order of lowest to highest frequency light?
radio waves, microwaves, infared, ultraviolet, x rays
what is the wavelength of an xray in comparison to a radiowave?
xrays have smaller wavelengths and higher frequencies while radio waves have longer wavelengths and lower frequencies
how are frequency and wavelength related
they are inversely proportional
to keep the speed of light constant and if the frequency increases then the wavelength must:
decrease
how is energy related to frequency
it is proportional
how is energy related to wavelength
it is inversely proportional
what does blackbody radiation describe
it describes the visible light that is emitted by hot metal
according to rayleighs law, what happens to the intensity if the wavelength is big? (IR)
the intensity will be very small, this works
according to rayleighs law, what happens to the intensity if the wavelength is small? why doesn’t this work?
the intensity should be large, this doesn’t work since we see a small intensity at the UV region
what is planck’s explanation for blackbody radiation
atoms are connected by springs and heat will cause springs to vibrate ONLY AT particular frequencies
what does it mean to say that energy only comes in particular amounts?
we say that energy is quantized
according to plancks explanation of blackbody radiation, what happens to the intensity when the wavelength is small
the intensity is also small
according to plancks explanation of blackbody radiation, what happens to the intensity when the wavelength is big
we get the same law as rayleighs law which stated that the intensity will be small
for black body radiation, when analyzing large things, how is the effect of quantum mechanics used?
it is insignificant and you get the same result as classical physics
for blackbody radiation, when analyzing small things, how is the effect of quantum mechanics used?
quantum mechanics is significant and necessary
what is the photoelectric effect
it is where electrons will be ejected from a metal when light is shined on its surface
for an electron to be ejected from a metal, what is the requirement?
the light frequency must be above a certain threshold
when electrons are ejected from a metal, how is the kinetic energy related?
it is linearly related to the applied frequency of light
for an electron to be ejected from metal, does it depend on the intensity of light?
no, it only depends on whether or not the frequency matches the threshold amount
why do electrons get ejected with light?
light acts as a particle and wave, meaning that it can collide with the electrons and eject them if it meets the energy requirements
what is the energy requirement for electrons to be ejected
the energy of the light must be greater than or equal to the binding energy of the electron/ the work function
how do we find the kinetic energy of an electron that has been ejected from a metal
energy of light- amount used to overcome work function
