P1 - Electromagnetic radiation and quantum phenomena Flashcards
what is the photoelectric effect?
what are the electrons emitted called?
When free electrons at or near the surface of a metal are emitted due to absorbing enough energy and vibrating more due to radiation being shined at it with high enough frequency.
Photoelectrons
What is the threshold frequency? (photoeletric effect)
The minimum frequency required for the electrons to be emitted
What does the maximum kinetic energy of the electrons released depend on? (photoelectric effect)
The maximum value of the kinetic energy increases with the frequency of the radiation
What is the intensity of radiation? (photoelectric effect)
The intensity of the radiation is the amount of energy per second hitting an area of the metal. The maximum
how does intensity of radiation affect the maximum kinetic energy of the photoelectrons?
Intensity of the radiation has no affect on the maximum kinetic energy of the photoelectrons
how does intensity of radiation affect the photoelectrons emitted per second?
The number of photoelectrons emitted per second is proportional to the intensity of the radiation
How does the photoelectric affect show that light cant just act as a wave?
wave theory says that for a particular frequency of an EM wave, the energy carried should be proportional to the intensity of the beam. However wave theory does not explain why there is a threshold frequency in the photoelectric effect
what is the work function?
before an electron can leave the surface of the metal, it needs enough energy to break the bonds holding it there this energy value is the work function.
How can you use 1/2 mv^2 in the photoelectric equation?
sue 1/2m velocity max squared as v is the maximum velocity of an electron.
What does irradiated mean?
light being shone onto
How do you find maximum kinetic energy using a stopping potential?
applying a ‘stopping potential’ p.d against the fastest moving electrons traveling with eKmax will give you a measure of maximum kinetic energy as the work done by the p.d is equal to the energy the electrons were carrying
what is stopping potential? (photoelectric effect)
the p.d applied to electrons traveling with eK max
which n level is referred to as the ground state?
when is an electron excited?
how does an electron change level? (n number)
n = 1
when it has an energy level greater than the ground state
when it emits a photon of a certain value, or absorbs an electron of a certain value
How does a fluorescent bulb work?
Fluorescent tubes use the excitation of electrons and photon emission to produce visible light. They contain mercury vapour, across which a high voltage is applied.
This high voltage accelerates fast moving free electrons that ionise some of the mercury atoms producing more free electrons. When the flow of electrons from the voltage collide with the mercury electrons the mercury electrons become excited to a higher energy level as energy is transferred.
As they then emit high energy photons equal to the energy difference between energy levels and can return to their ground states they release an a high energy photon in the uv range.
the electrons in the phosphor coating inside the fluorescent tube are excited, and releases visible light when the electrons return to its original energy state (de excite), which provides the glow in fluorescent lights.
How is light shown to act as a wave and a particle?
When a light beam is shone through a slit it diffracts like a wave and like how as waves the higher the frequency the wider the spread of the lines., the higher the voltage applied the the wider the spread of lines.
Photoelectric effect shows light as particles as the packets of photons act on induvial electrons on a 1 to one kind of way.
