Module 4 - Section 3 - Wave-particle Duality Flashcards
What shows light as a wave and why ?
Interference and diffraction show light as a wave - these two things can only be explained by waves interfering constructively or interfering destructively
What shows light acting like a particle ?
The photoelectric effect shows light behaving as a particle
Einstein thinks of a beam of light as a series of particle-like photons
If a photon is a discrete bundle of energy, then it can interact with an electron in a one-to-one way
All the energy in a photon is given to one electron
Whats Louis De Broglie’s wave particle duality theory
If ‘wave like’ light showed particle properties (photons), particles like electrons should be expected to show wave-like properties
Whats De Broglie’s equation ?
It relates a wave property ( wavelength ) to a moving particle property ( p,momentum )
Wavelength = h / p
What does electron diffraction show ?
It shows the wave nature of electrons
Where were diffraction pattern observed in electrons ?
Diffraction patterns are observed when accelerated electrons in a vacuum tube interact with the spaces between carbon atoms in polycrystalline crystal - the electron diffracts between the spaces of the carbon atoms. - this confirms that electrons show wave-like properties
In electron diffraction experiments, a smaller accelerating voltage i.e slower electrons gives…
Widely spaced rings
What happens if you increase the electrons speed in the electron diffraction experiment ?
The diffraction pattern circles squash together towards the middle - if the momentum is higher - then the wavelength is shorter and the spread of lines is smaller
In general Whats the wavelength of electrons accelerated in a vacuum tube ?
The wavelength is about the same size as electromagnetic waves in the x-ray part of the spectrum
How come particles don’t always show wave-like properties ?
This is because you only get diffraction if a particle interacts with an object of about the same size as its de Broglie’s wavelength
For example a tennis ball with a mass of 0.058kg and speed of 100ms-1 has a de Broglie wavelength of 10-34m that’s 1019 x smaller than the nucleus of an atom - and there iOS nothing really that small for the ball to interact with
What is somethings de Broglie wavelength ?
Wavelength = h/p
Electrons with a wavelength of around 1x10*-10 m are likely to be diffracted by the atoms in …
Polycrystalline structures
What does a shorter wavelength give ?
A shorter wavelength gives less diffraction effects
