Particles Flashcards
An antiparticle of the neutral lambda particle decays into a neutral pion and particle X. Identify X.
Anti-neutron.
The discover of particles such as a neutral lambda particle is made by large international research team. Suggest one reason for this.
Research requires funding from many different countries.
Quark structure for sigma+ particle.
uus
Deduce which particle, pi+ or Y, has a greater charge-to-mass ratio.
Charge is same for both particles
Y is a K meson
Pi+ has a greater charge to mass ratio
Discuss how the rate of loss of charge from the plate depends on the frequency and intensity of the incident radiation.
Loses its charge:
- uses electrons from the surface
- electrons carry away negative charge
Frequency:
- minimum energy for work function
- threshold frequency
Intensity:
- increase intensity= more photons per sec
- loses charge more rapidly on plate
What’s the photoelectric effect?
Photons of sufficient energy are absorbed by electrons on surface of metal hence liberating them
Explain why there is a current only if the frequency of the electromagnetic
radiation is above a certain value.
energy of **photon **
is greater than the work function
so electrons are emitted
1 joule is much larger than 1 electron-volt!
joules to eV equation
x1.6x10^19
State and explain the effect on the current when the intensity of the electromagnetic radiation is increased.
stopping potential would be greater
because the energy of the photons would be greater
maximum kinetic energy of electrons
would be greater
possible decay of antineutron
anti proton + positron + electron neutrino
State the names of the particles that are produced when a muon decays.
Electron + an electron antineutrino + muon neutrino
Identify the state of an electron in the energy level labelled 0.
free electrons
Explain why the energy levels are negative.
To become free, energy must be supplied.
Discuss how the discharge tube is made to emit electromagnetic radiation of specific frequencies. (6 marks)
A Reason for high potential difference:
* pd accelerates electrons
* electrons have to have sufficient energy to excite the atoms
**B Relation between spectrum and energy **
* Visible spectrum results from excited electrons moving into the lower level at -3.4 eV
* Each transition results in a photon of light
C Relevant calculation
* lowest frequency is due to a transition from the -1.5 eV level to the -3.4 level.
* Uses an energy difference to deduce one of the wavelengths: eg energy difference in J = 3× 10-19 = hc/E = 660 nm L
Describe how the variation of the strong nuclear force with distance contributes to thestability of the deuterium nucleus.
- up to 3-4 fm = attraction
- 0-0.5 fm = repulsion
- Prevent proton and neutron moving closer or further apart
