Materials and Quantum Flashcards
State Hooke’s law.
The extension of a material is directly proportional to the force applied to it, provided the limit of proportionality is not exceeded.
If you combine two springs in series…
Spring constant is halved, and extension is doubled.
If you combine two springs in parallel…
Spring constant is doubled, and extension is halved.
What does the area of a force/extension graph represent?
The energy.
What does the area under a stress/strain graph represent?
Energy per cubic meter.
Define elastic.
Material returns to its original shape after being deformed.
Define plastic.
Material doesn’t return to its original shape after being deformed.
What do materials experience past the elastic limit?
Plastic deformation; their shape will be permanently changed.
Toughest material means…
Greatest energy to break.
Why might the area beneath an unloading curve be smaller than the area under its corresponding loading curve?
Some of the energy put into the system is transferred as waste energy, such as heat.
Define the photoelectric effect.
Electrons liberated from the surface of a metal exposed to electromagnetic radiation above a minimum frequency.
Define work function.
The minimum energy required to liberate an electron from the surface of a particular metal.
Give two factors that can affect the work function of a metal.
How clean it is, and whether it had been oxidised or not.
Why do liberated electrons have a range of kinetic energies?
Electrons further away from the surface require some energy to reach the surface before they can be liberated.
Define stopping potential.
The electric potential required to stop electrons from leaving the surface. This is equal to the maximum kinetic energy.
Define threshold frequency.
The minimum frequency of electromagnetic radiation required to overcome the work function.
What produces emission and absorption spectra?
Gas discharge tubes.
What does each line in a spectra correspond to?
A photon with that specific energy, which is the difference between the energy levels of the atom.
How does a fluorescent bulb work?
- A flow of current excites atoms of mercury, which then de-excite to release photons.
- These photons then excite electrons in the atoms of the bulb coating, which then de-excite to release photons of visible light wavelength.
What image is formed from an electron diffraction tube?
Alternate rings of light and dark where constructive and destructive interference occurs.
Particles will only be diffracted if…
They interact with an object about the same size as its de Broglie wavelength.
Waves behaving like waves is shown by…
Diffraction.
Waves behaving like particles is shown by…
The photoelectric effect.
Particles behaving like particles is shown by…
Gas discharge tubes.
Particles behaving like waves is shown by…
Electron diffraction.
