Particles Flashcards
Give the charge and mass of a proton
+1.6 x 10^-19 (C)
1.67 x 10^-27 (Kg)
Give the charge and mass of a nutron
0
1.67 x 10^-27 (Kg)
Give the charge and mass of an electron
-1.6 x 10^-19 (C)
9.11 x 10^-31 (Kg)
Give the equation for specific charge
Charge/mass Or Q/m
Give the definition for an isotope
Atoms of the same element (same number of protons and electrons) but different number of nutrons
What are the forces acting on the nucleus
-Electrostatic repulsion between protons
-Gravity is very weak due to small masses
-Strong nuclear force binds all nucleons together. It is not associated with charge
-The nucleons are held in equilibrium position
Give the range of the strong nuclear force
It is repulsive below 0.5 fm
Between 0.5 - 3.0 fm it is attractive
Zero beyond 3.0fm
When does alpha decay take place
It only happens in very large nuclei like uranium. This is because nuclei are too massive for the strong nuclear force to keep them stable. An alpha particle is emitted from the unstable nucleus.
What is an alpha particle made of?
An alpha particle is made up of two protons and two neutrons ( same as a helium nucleus)
What is the range of an alpha particle
They have a very short range - only a few cm in air
Why do all alpha particles have the same kinetic energy?
All emitted alpha particles travel at the same speed which means they have the same ke
When does beta minus decay occur?
Beta minus decay occurs in nuclei that are neutron rich (high neutron to proton ratio)
What happens in beta minus decay?
A neutron in the nucleus changes into a proton. A beta particle (electron) and an electron anti-nutrino is emmitted from the nucleus.
It was first thought that the electron was the only particle emitted however it was found that the total energy after the decay was lees than before. This is why it was suggested that another particle, that had no charge and no mass was emmitted. The energy released is shared between the particles. This means the beta minus particle can have a range of Ke.
What is Gamma decay?
Gamma rays are emitted by nuclei that need to loose energy, normaly following alpha or beta decay.
There is no change in the proton or nucleon number and a new element is not formed.
What is a Geiger-Muller Tube?
It detects and records radiation. The background radiation is recorded before recording the radiation of a sorce then this is subtracted.
How does electromagentic radiation occur?
EM radiation can behave as a wave or a particle. This is known as wave-particle duality
What is a photon?
It is a fundamental particle. A photon is a massless “packet” or a “quantum” of electromagentic energy. This means that the energy is not transferred continously, but as discrete packets of energy.
How much energy does a photon have?
The energy of a photon is directly propertional to the frequency of the radiation.
E = hf
The photon energy equation can be combined with the wave speed equation v = fλ
this gives us another for of the photon energy equation: E=hc/λ
Give the definition for an electron volt
The energy gained by an electron that is travelling through a potential differance of one volt.
Why is an electron volt used?
When dealing with small energy values, it is often more useful to use an alternative energy unit to joules. e.g electron volts(eV)
How do you convert from electon-volts to joules?
x1.6x20^-19
How do you convert from joules to electron-volts?
÷ 1.6x10^-19
What is antimatter/antiparticles?
for every particle ther is a corresponding antiparticle.
They have the same mass and rest energy.
They have the opposite charge.
They also have other opporsite properties such as baryon number, lepton number and strangness.
What is energy mass equivelance?
-energy can be converted into mass
-mass can be converted to energy
