What can happen if you shine light of a high frequency onto a surface of metal?
What is the name of this phenomenon?
For most metals, in which range is the frequency of light in the photoelectric effect?
In the photoelectric effect, what happens to the free electrons on the surface?
-Absorb energy from light, making them vibrate
At what stage can the metal surface emit electrons?
-If an electrons absorbs enough energy to break away from the bonds in the metal holding it.
In the photoelectric effect, what is the name for the electrons being emitted?
What is the threshold frequency?
-For a given metal, the minimum frequency of radiation needed to emit photoelectrons
What is the relationship between frequency of radiation and maximum kinetic energy of photoelectrons?
-Maximum kinetic energy increases with frequency of radiation
What is the relationship between maximum kinetic energy and intensity of radiation?
-Maximum kinetic energy is unaffected by intensity of radiation
What does the intensity of radiation depend on?
-Number of photoelectrons emitted per second
What puzzled scientists about the photoelectric effect?
-Couldn’t be explained by wave theory i.e. there is no explanation for threshold frequency
Using wave theory, what would kinetic energy of particles be proportional to?
According to wave theory, for a particular frequency of light, the energy carried is proportional to the ********* of the beam.
What was Max Planck investigating?
-Black body radiation
What did he suggest?
-EM waves can only be released is discrete packets, or quanta
What was the formula for the energy carried by one of the wave packets?
-E = hc/λ
What is h? What is its value?
-6.63 × 10-34 Js
What is c? What is its value?
-Speed of light in a vacuum
-3.00 × 108 ms-1
What did Einstein further suggest about EM waves?
-Only exist in discrete packets, called photons
How did Einstein describe the photons interacting with an electron in a metal surface?
-Photons of light having a one-on-one, particle like interaction with an electron in the metal surface. It would transfer all its energy to that one, specific electron
Use the photon model to concisely explain the photoelectric effect (2 marks)
-When light hits its surface, the metal is bombarded by photons
-If one of these photons collides with a free electron, the electron will gain energy equal to ‘hf’
What must happen before an electron can leave the surface of the metal? What is this called?
-Enough energy to break the bonds holding it there
-This energy is called the WORK FUNCTION ENERGY (φ)
What is the Greek symbol for WORK FUNCTION ENERGY (φ)? Where is it placed in the Greek alphabet?
If the energy gained from the photon is g****** than…