C13 (Quantum Physics)

Question 1

Einstein proposed that although light exhibits wave-like properties, it travelled…

Answer 1

It travelled in particles called photons

Question 2

Photons contain discrete “energy packets” called..

Answer 2

Quanta

Question 3

The energy of each quanta depends on what?

Answer 3

Depends on the frequency of the light

Question 4

What has the development of quantum physics led to

Answer 4

Understanding how we can use different models to describe EM radiation
E.g use the photon model to explain how EM radiation interacts with matter, and the wave model to explain its propagation through space.

Question 5

The energy of each photon is directly proportional to what

Answer 5

To its frequency

Question 6

Equation for the energy of a photon

Answer 6

E= hf

h- planks constant (6.63x10^-34)

Question 7

The general speed of a wave through a vacuum

Answer 7

3x10^8

Question 8

Equation for energy of a photon (mixed with the wave speed equation)

Answer 8

E= hc / lamdar

Question 9

Energy of photon is inversely proportional to

Answer 9

Wavelength

Question 10

Instead of using joules we often use another unit when measuring energies at a quantum scale

Answer 10

The electron volt (eV)

Question 11

1 eV is equal to what

Answer 11

1.60x10^-19

Question 12

Electrical energy equation

Answer 12

Ee=eV

Question 13

How can you work out planks constant

Answer 13

Do a simple experiment with LEDs to determine a value for the plank constant by considering the energies of the photons they emit.

Question 14

What is photon electric emission

Answer 14

The release of an electron when a photon of light hits the metal surface the electron is on.

Ultra violet light causes the zinc to emit electrons (releases more than visible light as it has a shorter wavelength and a higher frequency, and therefore more energy).

Question 15

Work function

Answer 15

The amount of energy needed to release an electron from a metal
(Generally, work functions are lower for more reactive metals).

Question 16

Photon energy equation (involving work function)

Answer 16

Photon energy= work function + KE of electron

Question 17

Equation for work function (when KE=0)

Answer 17

E= work function = h x fo

fo (min freq required to release an electron)

Question 18

Equation for max KE

Answer 18

Ek= hf -work function 
Ek= hf - hfo

Question 19

Conclusions for photoelectric effect (4):

Answer 19

• For given metal no photon electrons are emitted if the radiation has a frequency below a certain value (the threshold frequency).
• The maximum KE of photoelectrons is unaffected by the intensity of radiation
• The number of photoelectrons emitted is proportional to the intensity
• The max KE of photoelectrons increases with the frequency of the radiation

Question 20

Wave properties of particles (what did De Broglie suggest):

Answer 20

De Broglie suggested that all particles could behave as waves. He deduced that a particle has a wavelength, and it was dependent on only the momentum of the particle.

Question 21

De Broglie equation

Answer 21

Wavelength = h / p = h / mv

Question 22

Evidence of wave like properties of light

Answer 22

Diffracts
Refracts
Reflects
Polarisation

Question 23

Evidence of particle like properties for light

Answer 23

Photoelectric effect

Reflection