Quantum Physics/Nature of light IAL edexcel

Explain what is meant by a photon.

a discrete packet of energy of the electromagnetic spectrum

Define work function

the minimum energy required to remove an electron from the surface of a material (metal)

define line spectrum

what are the 2 types of line spectrum?

- a spectrum containing a pattern of discrete lines at discrete frequencies
(or wavelengths)

- it is produced by emission or absorbtion of (radiation) at discrete frequencies by atoms
(or molecules or hot gases)


- emission and absorption spectrum

Explain how line spectra provide evidence for the existence of energy levels in atoms (4marks)

• when electrons become excited they rise to higher energy level

• (however at higher energy level they are unstable so) electrons then drop down to lower energy level
  
  

• thus emitting energy as photon with discrete frequency, the energy of photon is equal to change in energy level
  
  

• E = hf
  
  

• thus only discrete frequencies can be observed in a line spectra, this means that energy levels are discrete
  (therefore proving existence…)

what happens when electrons:
absorb energy as photons
at emission spectrium

absorbs energy = they get excited and rise to higher energy level

emission spectrium = drops to lower energy level and emits photon


NOTE:
The energy (and frequency) of the photon is equal to the energy difference