Physics Unit 10 Study Guide
pair production
A photon can actually create matter. Antimatter has the same mass but opposite charge. The photon disappears in the process of creating the electron position pair. E = mc^2
photon-matter interactions
A photon is a packet of energy and its energy is found via the equation E = hf.
X-Ray production and diffraction
An x-ray is a form of electromagnetic radiation of very short wavelength.They are produced when high-speed electrons, accelerated by high voltage in an evacuated tube, strike a glass or metal target. They knew that x-rays weren't charged particles because they didn't respond to a magnetic field. X-rays can be diffracted from many possible planes within a crystal. KE electron = E photon = hf An x-ray is an electromagnetic radiation that is produced via the reverse of the photoelectric effect so that an electron is thrown towards a piece of metal and the electron and proton bounce off.
frequency and energy of a photon (E = hf)
E photon = KE electron + W 0
Einstein's explanation for the photoelectric effect
Einstein extended Planck's concept of quantization to electromagnetic waves. He assumed that the energy of light is not distributed evenly over the whole expanding wave front, but is concentrated in separate packets of energy called photons. All of the photon energy is transferred to the electron and the photon ceases to exist. Since electrons are held in the metal by attractive forces, some energy. W0 is required to get an electron out through the surface.
transitions between energy states/ energy of photons
Electrons has energy levels in atoms. Absorbed photons: go up,has to go in one step because multiple is too unstable Emitted photons: go down, can go down in steps E = hf Ionization energy is another name for work function W0.
Energy level diagrams
Electrons have energy levels in atoms. The photons that are absorbed are the ones that go up and can do up in step because it is too unstale. Photon emission occurs when the level goes fdown and the electron can go down in steps. Frequency of emitted photons = E = hf The ionization of energy is also referred to as the work function. This is the threshold level required for the photoelectric effect.
maximum kinetic energy of photoelectrons
KE electrons = E photons - W0 = hf - hf0
work function and threshold frequency
W 0=hf0
compton effect
a single photon of wavelength strikes an electron in some material, knocking it out of its atom. The scattered photon has less energy and has a longer wavelength. E = E' + KE hf = hf' + qV
photoelectric effect
any metal may exhibit the photoelectric effect, but only if the incident light has a frequency greater than the threshold frequency, which depends on the material being illuminated. If the light frequency exceeds the threshold frequency, a photoelectric effect is observed and the number of photo-electrons emitted is proportional to the light intensity. The maximum kinetic energy of the photo-electrons is independent of light intensity. The maximum kinetic energy of the photo-electrons increases with increasing light frequency. Electrons are emitted from the surface almost instantaneously. The photoelectric effect is when a photon strikes metal and an electron gets ejected. It occurs only if the photon has a threshold frequency or a high enough frequency. It does not matter how intense the light is. The photon has to have enough energy. The kinetic energy of a photo-electron depends on the energy/frequency coming in. The frequency of the incident photon. Once this effect occurs the current depends on the intensity of light. The effect occurs almost instantaneously once a photon hits the metal. Equation: KE = E - W0 1/2 mv^2 = hf - hf0 = qV
Michelson-Morley Experiment
designed to measure the speed of the ether (the medium in which light was assumed to travel) with respect to the earth. A light beam was sent in three dimensions and reflected back. One would anticipate a difference in speed if the earth was moving through an ether, however, no significant difference in speed was observed, so the either does not exist. Wanted to find the speed of ether but found that it was the same speed in all directions.
wave particle dualism
electronmagnetic waves and matter exhibit both characteristic
bohr model of atom
for any given atom,the electrons can exist in one of several stationary states (or orbitals) with no emission of radiation. Any emission or absorption of radiation,either as visible light or other electronmagnetic radiation, corresponds to a sudden transition between two such stationary states. The radiation emitted or absorbed has a frequency, f, determined by E = E upper states - E lower state hf = E upper state - E lower state
particle nature of electromagnetic waves
momentum of particle: p = mass x velocity momentum, photoelectric effect,reflection
Pauli Exclusion Principle
no two electrons in an atom can occupy the same quantum state. No two electrons can occupy the same energy label/orbital.
momentum of a wave
p = h / wavelength
wave nature of matter
reflection, refraction, diffraction, polarization,interference, and wavelength.
Energy Equivalent of mass (E = mc^2)
the rest mass of an object is a measure of its energy content E = mc^2
Heisenberg Uncertainty Principle
to make a measurement of an object without disturbing it,at least a little, is not possible. There is a limit to the accuracy of certain measurements. We cannot measure both the position and momentum of an object precisely at the same time. You can't know the position and speed of a particle at the same time
wave function and probability
wave function: amplitude of wave probability: predict the majority of what's going to happen determinism: we can know precise measurements
de Brogile wavelength of a particle/momentum of a particle
wave nature of matter: de broglie wavelength of a particle/momentum of a particle wavelength= h /mv
