wave particle duality

Question 1

what shows light as a wave

Answer 1

interference and diffraction

Question 2

what does light produce that proves it is a wave

Answer 2

interference and diffraction patterns - alternating bands of dark and light

Question 3

how can these only be explained

Answer 3

by using waves interfering constructively or interfering destructively

Question 4

what shows light behaving as a particle

Answer 4

photoelectric effect

Question 5

how did Einstein explain the results of the photoelectric effect

Answer 5

by thinking of the beam of light as a series of particle light photons

Question 6

what does it mean if a photon is a discrete bundle of energy

Answer 6

then it can interact with an electron in a one-to-one way. all the energy in the photon is given to one electron

Question 7

who came up with the wave particle duality theory

Answer 7

de broglie

Question 8

what was his suggestion

Answer 8

if a wave-like light showed particle properties (photons) then particles like electrons should be expected to show wave-like properties

Question 9

how does de broglie relate a wave and particle property

Answer 9

he relates wave property (wavelength) to a moving particle property (momentum)

Question 10

what is the formula for de broglie wavelength

Answer 10

lambda = h/mv

Question 11

what can the de broglie wave of a particle be interpreted as

Answer 11

a probability wave

Question 12

what proved the wave nature of electrons

Answer 12

electron diffraction

Question 13

when are diffraction patterns observed

Answer 13

when electrons are accelerated in a vacuum tube interact with the spaces in a graphite crystal

Question 14

what should happen according to wave theory

Answer 14

the spread of the lines in the diffraction pattern increases if the wavelength of the wave is greater

Question 15

was this proven in electron diffraction experiments

Answer 15

a smaller accelerating voltage (slower electrons) gave more widely spaced rings so yes

Question 16

what is the conclusion

Answer 16

increasing the electron speed (and therefore electron momentum) makes the diffraction pattern squash together towards the middle

Question 17

what happens to wavelength if the momentum is greater

Answer 17

the wavelength is shorter and the spread of lines in smaller

Question 18

when do you only get a diffraction pattern

Answer 18

if a particle interacts with an object of about the same size as its de broglie wavelength

Question 19

how did scientists understanding of nature and matter change over time

Answer 19

through process of hypothesis and validation