Particles and Quantum Phenomena Flashcards
What are isotopes?
Same proton number but different number of neutrons.
What is specific charge?
Charge per unit mass.
What are ions?
Loss or gain of 1 or more electrons.
Strong Nuclear Force and Range
-Only attractive between 0.5 fm and 3 fm.
-Repulsive less than 0.5 fm.
More than 3 fm its weak/ short range.
What are EM waves (electromagnetic waves)?
-They are transverse waves.
-They oscillate perpendicular to each other and the direction of travel.
What are the Orders of EM waves?
Lowest Frequency, Highest Wavelength:
-Radio
-Microwave
-Infrared
-Visable Light
-Ultraviolet
-X-rays
-Gamma Rays
**Highest Frequency, Lowest Wavelength
What is eV?
Unit for energy.
How do you convert from eV -> J?
EV-> J is dividing by 1.6x10^-19.
How do you convert to eV-> J?
By multiplying eV by x1.6x10^-19
What are Photons?
A quantised packet of EM energy.
What is rest mass?
Mass of an object/ particle when it’s stationary.
What is rest mass energy?
Energy equivalent to the mass of a stationary particle.
What is pair production?
When a high energy photon converts into the particle and antiparticle.
What is annihilation?
When a particle and antiparticle collide there masses are converted into energy in the form of 2 gamma photos travelling in the opposite direction to conserve momentum.
What is the Strong nuclear force?
- Strongest
-Hadrons only
-Holds nucleus together
-Short range 3fm.
-Strange particles produced.
Exchange Particle:
-Gluon and Pions
What is the Electromagnetic Force?
-Acts on charged particles.
Exchange Particles
-Virtual Photons
What is the weak nuclear force?
-Acts on a particle.
-Very short range (0.001 fm)
-Causes radioactive decay.
Exchange Particles:
-W Boson.
What must all been conserved?
-Momentum
-Energy
-Charge
-Baryon Number
Lepton Number
What is intensity?
Power per unit area.
What is the photoelectric effect?
Emission of electrons from a metal surface when light above a threshold frequency is incident on the metal.
What is the work function?
The minimum energy required for an electron to escape from a metal.
What is the threshold frequency?
Minimum frequency of light which causes electrons to be emitted from the surface of a metal.
How to change the maximum kinetic energy?
Increasing the frequency, decreases the wavelength.
Effect:
-Electron comes out with a higher max energy.
Change the metal!
-lowers work function
Effect:
-Minimum energy for an electron to escape will be lower comes out with a higher kinetic energy.
Why are electrons emitted with a range of kinetic energies up to a maximum?
-Delocalised electrons in metal have a range of energies.
-Electrons near the surface have the most energy therefore require the least to escape.
-Emitted with the highest kinetic energy.
Electrons deeper in the metal have the less energy so require more energy to escape the metal.
Same wavelength, more intensity of light.
Effect:
-More electrons emitted
-Photon has same energy
What happens when you increase brightness without a colour change and explain the effect of electron emitted?
- Number of photons increased.
- It’s a 1 to 1 interaction.
- More electron emitted.
- Same energy therefore work function unchanged.
-Maximum kinetic energy of electrons doesn’t change.
What happens when wavelength decreases without changing intensity? Explain why current increases then decreases as wavelength is shortened.
- Wavelength decreases, energy of the photon increases.
- More electrons are emitted.
- Electrons are emitted with maximum kinetics energy.
- Intensity is constant,photons number per time must decrease.
What is ionisation by collision?
- Collision of free electrons with atomic electrons.
- Free electron transfers its kinetic energy to the atomic electron.
- Atomic electro now has enough energy to leave the atom completely.
- A charged atom is formed.
What is ionisation by photon?
- Atomic electron absorbs energy from a photon.
- Enough energy from photon for an electron to leave the atom.
What is excitation by collision?
- Collision of free electrons with atomic electrons.
- Free electron transfers all kinetic energy to atomic electron.
- Energy gained corresponding to the difference in energy levels.
- Atomic electron moves to a higher energy level.
What is De-excitation?
- Move from higher energy to a lower energy level.
- Emits a photon.
How do filament lamps work?
-Current in a filament causes it to heat up, electrons are emitted.
- Electrons are accelerated by a potential difference and collides with electrons in the mercury atom.
- Transfers energy which causes atomic electrons in the mercury atom to excite and de-excite.
- When de-excitation occurs a UV photon is emitted.
- The UV photon absorbed by phosphor electrons and excites it.
Then de-excites it 2 times visable photons are emitted.
What is wave-particle duality?
Physical entities can show wave-like or particles like properties.
