AQA A GCE Physics - Electromagnetic Radiation and Quantum Phenomena

What can happen if you shine light of a high frequency onto a surface of metal?

-Emit electrons

 

What is the name of this phenomenon?

-Photoelectric Effect

 

For most metals, in which range is the frequency of light in the photoelectric effect?

-Ultraviolet range

 

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?

-Photoelectrons

 

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?

-Intensity

 

According to wave theory, for a particular frequency of light, the energy carried is proportional to the ********* of the beam.

-Intensity

 

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?

-Planck’s constant

-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?

-Phi

-21^st

 

If the energy gained from the photon is g****** than…