Wave-particle duality

Question 1

Idea of wave particle duality

Answer 1

Light can act both like a particle and a wave

Question 2

Photoelectric effect

Answer 2

When electrons are emitted from a metal when light of a large enough frequency hits the metal

Question 3

What wavelengths and frequency cause the photoelectric effect

Answer 3

Low wavelengths and high frequency

Question 4

Why when using a photocathode is a quartz window used

Answer 4

It does not absorb the radiation whereas something like glass would.

Question 5

What would happen if air was in photocathode as opposed to vacuum

Answer 5

Electrons will be ionised and absorbed by air

Question 6

What happens if the intensity of light is increased at a frequency below threshold ?

Answer 6

No electrons will be emitted - no change

Question 7

What happens if the intensity of light is increased above the threshold

Answer 7

More electrons will be emitted per second when intensity (irradiance) increases

Question 8

How does the photoelectric effect show that light behaves as a particle?

Answer 8

In this situation since high frequency but low intensity will emit electrons- but low frequency high intensity doesn’t emit electrons

Question 9

Beam of light can be thought of as

Answer 9

A stream of particles called photon

Question 10

Energy of a photon equation

Answer 10

E=hf
Where E is energy in joules
f Is frequency in Hz
h is plancks constant

Question 11

Plancks constant

Answer 11

h - 6.63x10^-34

Question 12

Threshold frequency of a photon

Answer 12

fo (f nought) minimum frequency of photon to eject electron from atom

Question 13

Explanation of photoelectric effect

Answer 13

Photon of light can be absorbed by one electrons only, if the energy the photon contains is large enough to allow the electron to escape the atom, the electron will be ejected

Question 14

Greater intensity of light =

Answer 14

Greater number of photons per second

Question 15

What happens when f of photon is greater than fo

Answer 15

The photon will have more energy than that required to eject the electron, the electron will have more energy when outside the atom - as such it will move once it is out

Question 16

Energy of photon in terms of wavelength

Answer 16

E=hc/lamba c is speed of light

Question 17

Einstein’s photoelectric equation (calculates energy of the electron once out the particle too)

Answer 17

hf = hfo + 1/2meve^2
me = mass of electron
ve = velocity of electron once out of the atom

Question 18

Work function

Answer 18

Minimum energy required to produce a photoelectron (hfo)

Question 19

Different metals have

Answer 19

Different threshold frequency’s