3.6 Wave-particle duality

Question 1

What does it mean if a particle has a dual nature?

Answer 1

» It can behave as a wave or as a particle according to circumstances

Question 2

When is the wave-like nature of light observed?

Answer 2

» Diffraction of light takes place

Question 3

What experiment can show the wave like nature of light?

Answer 3

» When light passes through a narrow slit
» The light emerging from the split spreads out in the same way as water waves spread out after passing through a gap

Question 4

What 2 factor affect diffraction?

Answer 4

» Narrower the gap - increases diffraction
» Longer the wavelength - increases diffraction

Question 5

When is the particle-like nature observed of light?

Answer 5

» In the photoelectric effect
» As the electron absorbs a single photon of frequency f

Question 6

What is the evidence that electrons have particle-like nature?

Answer 6

» When electrons in a beam can be deflected by a magnetic field

Question 7

Who proposes that matter particles can also have wave like nature?

Answer 7

» Louis de Broglie

Question 8

What were the 2 main factors of Broglie’s hypothesis?

Answer 8

» Matter particles have a dual wave particle nature
» Wave like behavior’s is characterized by a wavelength, it’s de Broglie wavelength
» Which is equal to h/p

Question 9

What is the equation for de Broglie wavelength?

Answer 9

» Wavelength = h/mv

Question 10

How can the de Broglie wavelength of a particle be altered?

Answer 10

» By changing of the velocity of the particle

Question 11

What does it mean by the duality of electrons?

Answer 11

» Electron can behave as a particle and a wave

Question 12

Give one example of each type of behaviour of electrons

Answer 12

» Electron behaving as a wave - interference
» Electron behaving as a particle - Deflected by a magnetic field

Question 13

What is Broglie’s theory?

Answer 13

» All particles have aspects of both a particle and a wave, they all exhibit quantum behaviour

Question 14

What are 2 evidences which show light is a wave?

Answer 14

» Interference
» Diffraction

Question 15

Why is it esaier to demonstrate the wave properties of electrons than to demonstrate the wave properties of protons?

Answer 15

» Electrons have smaller mass, using de broglie’s equation, a small mass means a higher wavelength, which is more observable when compared to a proton

Question 16

Why do electrons lose energy in excitation?

Answer 16

»Collision causes a transfer of kinetic energy, which causes excitation