section 1 and 2 aqa Flashcards
particles, EM radiation and Quantum phenomena.
Explain what causes extra particles to be created when two particles collide.
Energy and mass are equivalent. When two particles collide, there is a lot of energy at the point of impact. This energy is converted to mass.
which mesons is stable?
none as all mesons are unstable.
what is the lightest meson?
Pions.
where was Pions and kaons discovered?
Cosmic rays.
through what interaction do mesons and baryons interact
strong force
what are leptons?
Leptons are fundamental particles that do not feel the strong nuclear force. They only really interact through the weak interaction (along with a bit of gravitational and electromagnetic force as well if they change).
List all the decay products of the neutron. Explain why this decay cannot be due to the strong interaction.
Proton, electron and a electron anti-neutrino.(1MARK) The electron and the electron anti-neutrino are leptons.(1 MARK) Leptons are not affected by the strong nuclear force ,so the decay cant be due to the strong interaction.(1 MARK).
write the quark composition of pi minus
ûd
HOW DOES A FLORESCNET TUBE WORK
Turn on the power supply which causes a high voltage to be applied to the mercury vapour which accelerates fast free electrons which collide with the mercury atoms.
mercury electrons are then excited ,returning to ground state and UV light photons are released.
The tubes phosphorus coating absorbs UV photons and its electrons are excited , They cascade down the energy levels and visible light photon is released.
Describe the photoelectric effect.
When light above a particular frequency is shone on metal , electrons are released - these released electrons are “ photoelectrons
“.
what is the threshold frequency?
The minimum amount of frequency required for electrons to be emitted from the metals surface.
why does a photon need to be of a minimum frequency to liberate an electron?
The energy of a photon is determined by its frequency , the photons energy must be greater than the work function in order for an electron to be emitted.
if a photon has a frequency higher than the threshold frequency , what would occur?
The electron will be liberated and the remaining energy is the kinetic energy of the electron.
if light is incident on a metal and photoelectric effect does NOT occur ,what is the effect on increasing the intensity?
- if it is more intense then there would be more photons incident on the metal each second.
-However each photon still has the same amount of energy as before.
-Therefore it still does not contain enough energy to liberate an electron.
-No effect
Define the work function.
The minimum energy required by an electron to overcome the metallic bond holding it in the metal.
What is an electron volt?
The kinetic energy of an electron that has been accelerated from rest through a potential difference of 1v
How do electrons in Atoms exist?
Electrons in atoms exist in discrete levels.
How can electrons move down energy levels?
electrons can move down energy levels by emitting a photon
How can electrons move up energy levels?
electrons can move up energy levels if they absorb a photon with the exact energy difference between the two levels
What is the movement of an electron to a higher energy level called?
excitation.
if an electron is removed from an atom what do we call this?
ionisation
what is the ionisation energy
the energy needed to completely remove an electron from an atom from ground state(n=1)
How to get line emission spectrum using fluorescent tubes?
-if you split the light from a fluorescent tube using a prism or a diffraction grating, you will get a line spectrum.
-Each line corresponds a particular wavelength of light emitted by the source
-since only certain photon energies are allowed, you only see the wavelength corresponding these energies.
How can we get an Absorption spectrum
By shining white light through cool gas.
describe a line emission spectrum
- series of bright lines against a black background
describe how continuous spectra contains all possible wave length.
-the spectrum of white light is continuous.
-if you split the light up with a prism ,the colours are merged into each other (there aren’t any gaps in the spectrum).
-Hot things emit a continuous spectrum in the visble and infared
-All the wavelengths are allowed because the electrons are not confined to energy levels in the object producing the continuous spectrum. The electrons are not bound to atoms and are free.
describe a absorption spectrum.
a continuous spectrum with black lines in it, corresponding to the absorbed wavelengths.
define excitation
when an electron moves from a lower energy level to a higher energy level by absorbing energy.
which observation show light to have a ‘wave-like’ character ?
interference and diffraction
which observation show light to have a ‘particle’ character ?
the photoelectric effect
What happens to the de Broglie wavelength of a particle if its momentum increases?
How does this affect the particles diffraction pattern?
as the particles momentum increases the De Broglie wavelength decreases .
This means the particles angle of diffraction decreases, and the radius of the diffraction pattern decreases
which observation show electrons to have a ‘wave-like’ character ?
electron diffraction
Nodes
A point of minimum or no disturbance(basically amplitude is = 0/no vibration occurs its a fixed point).
Anti-Nodes
point with maximum amplitude(at this point it goes up and down
tensile stress
Force exerted per unit cross-sectional area
tensile strain
ratio of extension to original length
area under a force extension graph
energy stored(work done) per unit volume
A iodine-125 nuclide decays by an electron capture to form a tellurium nuclide.
state two differences between the constituents of the iodine nucleus and the tellurium nucleus it decays into.
electron capture: proton absorbs an electron ,neutron is formed.
tellurium nuclide has 1 more neutron.
tellurium nuclide has 1 less proton
Q: Why do large nuclei (like 208-Pb z=82) have more neutrons than protons?
(Refer to forces, range, and affected particles)
Strong nuclear force holds nucleus together, acts on protons and neutrons, short range (~3 fm).
Electrostatic (Coulomb) repulsion acts between protons, infinite range.
In large nuclei, more neutrons are needed to add strong nuclear force to overcome proton repulsion and keep the nucleus stable.
