The Photoelectric Effect

Question 1

What is the Photoelectric Effect

Answer 1

when radiation of a high enough frequency is shone onto the surface of a metal it will instantly emit electrons becausee of the way atoms are bonded together in metals free electrons on or near the surface vibrate due to absorbed radiation and the bonds holding it to the metal break causing the electron to be released

Question 2

what are electrons emitted by the photoelectric effect called

Answer 2

photoelectrons

Question 3

what are the four conclusions from the photoelectric effect

Answer 3

1. for a given metal no photoelectrons are emitted if the radiation is below a certain frequency called the threshold frequency
2. photoelctrons are emitted with various kinetic energies ranging from zero to the maximum which increases with the frequency of radiation
3. the intensity of radiation is the amont of energy per second hitting an area of metal, this does not effect the maximum kinetic energy of the photoelectrons
4. the number of photoelectrons emitted per second is proportional to the intensity of the radiation

Question 4

what cannot be explained if Em radiation only acts as a wave

Answer 4

electrons are only emitted when the wave is above threshold frequency
kinetic energy depends only on the frequency in the photoelctric effect

Question 5

what is the equation for threshold frequency

Answer 5

threshold frequency=work function/plancks constant

Question 6

what is the equation for maximum kinetic energy of a elctron

Answer 6

maximum kinetic energy =1/2 x mass x maximum velocity squared

Question 7

what is the equation linking stopping potential electron charge and maximum kinetic energy

Answer 7

electron charge x stopping potential = maximum kinetic energy

Question 8

how many joules is one electron volt

Answer 8

1eV = 1.6 x 10^-19 joules

Question 9

what is the movement of an electron to a higher energy level called

Answer 9

excitation

Question 10

what is the equation for the change in energy when an electron moves between two energy levels

Answer 10

Energly lvl 1 - Energy lvl 2 = change in energy = hf

Question 11

what is ionisation

Answer 11

when an lectron has been removed from an atom the atom is ionised

Question 12

what is the ionisation energy of an atom

Answer 12

the amount of energy required to remove an electron from the ground state atom

Question 13

how is photon emission used in fluorescent tubes

Answer 13

in fluorescent tubes excitation of elctrons and photon emission is used to produce visible light

Question 14

what is diffraction

Answer 14

when light passes through a narrow gap it spreads out

Question 15

what two things show light acts as both a particle and a wave

Answer 15

the photoelectric effect and diffraction, this is a phonomenon know as wave particle duality

Question 16

what is the equation for de broglie wavelength

Answer 16

de broglie wavelength=mass x velocity x plancks constant