Wave Particle Duality

Question 1

what is meant by wave-particle duality?

Answer 1

• phenomenon in which light can behave as a particle and a wave

Question 2

explain why wave theory of light does not support the idea of a threshold frequency

Answer 2

• wave theory suggests that any frequency of light can give rise to photoelectric emission if the exposure is long enough

• this is because wave theory suggests the energy absorbed by each electron will increase gradually with each wave

• also the kinetic energy of the electrons should increase with radiation intensity but this is not the case

Question 3

how does electron diffraction work?

Answer 3

• electron beam must be focused through a gap in similar size to its De Broglie wavelength.

• graphite film is ideal for this purpose because of its crystalline structure

Question 4

what was the diffraction pattern observed on the screen

Answer 4

• a series of concentric rings were present

• a larger accelerating voltage reduces the diameter of the concentric rings

• a smaller accelerating voltage increases the diameter of the concentric rings

Question 5

what is the equation for the De Broglie Wavelength? ( $ )

Answer 5

$ = h / p
$ = h / mv

E = 1/2 mv^2 so p^2 / 2m
so p = root 2mE

$ = h / root 2mE