4.5 Quantum Flashcards
(8 cards)
1
Q
What are photons
A
Particles of light
2
Q
What are photons sometimes referred to as?
A
A quantum of energy of EM radiation. A quantum in this context just means a set (finite) amount
3
Q
T or F: energy of a photon is proportional to the wavelength of the light
A
F
It’s proportional to the frequency: E = hf
Energy is inversely proportional to wavelength
4
Q
What is energy inversely proportional to?
A
Wavelength
5
Q
What is ‘h’ in the equation E=hf? Give units
A
Planck constant, J
6
Q
What is Planck’s constant?
A
6.63 X 10^-34
7
Q
What quantity can be measured in electron volts (eV)?
A
Energy
8
Q
Describe an experiment which can be used to estimate the Planck constant
A
- an LED will only allow current to pass after a min voltage has been put across it
- at this voltage, all electrons will have the same energy as a photon emitted by the LED (which you will know the frequency of)
- find the threshold voltage by seeing when the current flows in the circuit can then be used to find h from h = E/f
