Ultrasound is a longitudinal wave with a frequency greater than 20kHz. It is non-ionising, non-invasive and quick. Ultrasound used in medical imaging typically has frequencies of 1-15MHz, arriving in pulses with a frequency of 5kHz. It is generated and detected by...
X-rays are high energy photons with short wavelengths, range 10-8 to 10-13m. They are produced in X-ray tubes: Evacuated tube containing two electrodes (evacuated so electrons pass through without interacting with gas atoms) An external power supply is used to create...
Medical tracers such as technetium-99m and fluorine-18 can be used as diagnostic tools. Inject tracer (into bloodstream) Taken up by organ or shows blockage By emitting radiation detected by camera More specifically, tracers may be used to: Monitor blood flow in...
Einstein’s mass-energy equation describes how mass and energy are interchangeable quantities. Conservation of mass-energy can also be used to explain radioactivity phenomena: when energy is released in the KE of an alpha or beta particle (or the energy of a gamma...
Radioactive decay is random and spontaneous. Random: cannot be predicted; each atom has the same chance of decaying in a given time interval 2. Spontaneous: not affected by external factors like pressure or the presence of other nuclei in the sample 3 types of...
Each particle has a corresponding antiparticle with the same mass but opposite values for all other properties (e.g. strangeness, charge). Examples of particle-antiparticle pairs include: electron-positron, proton-antiproton, neutronantineutron,...
Rutherford’s alpha-scattering experiment provided evidence of a small, charged nucleus. A narrow beam of alpha particles, all of the same kinetic energy from a radioactive source were targeted at a thin piece of gold foil which was only a few atomic layers thick. The...
When a conducting rod moves in a field, the electrons experience a force so accumulate at one end. This induces an emf across the ends of the rod. An emf can be induced in a flat coil or solenoid by moving he coil towards or away from the magnet’s poles, or moving a...
The force on a charged particle travelling at right angles to a uniform magnetic field is given by: According to Fleming’s left hand rule, the force experienced by the particle is always perpendicular to its direction of motion. This is the condition for circular...
Magnetic fields are regions where a force is exerted on magnetic materials. They are created by moving charges and permanent magnets. Magnetic fields can be mapped by magnetic field lines, which pass from north to south, The closer the lines, the stronger the field....
Electric potential energy is given by the formula This result is obtained by integrating the force-distance graph because work done is equal to the area under the graph. Electric potential is the electric potential energy experienced per unit charge. Therefore, it...
The electric field strength of a uniform electric field is given by: Derivation: The units of electric field strength can therefore be given as This also yields some equations of capacitance: Where is the permittivity of free space and ε is the relative...
Coulomb’s law can be applied to any point charges. It is given by: Since , it follows that, for a point charge, the electric field strength is given by: Gravitational and electric fields show some similarities and differences: ...
Fields are regions in which an object will experience a force at a distance (non-contact force). An electric field is created by charged objects. A uniformly charged sphere can be modelled can be modelled as a point charge at its centre. Electric field lines map...
The capacitance of a parallel plate capacitor depends on the separation between the plates and the area of overlap between them. Where is the permittivity of the dielectric, given by = 0 (where 0 is the permittivity of free space and is the relative permittivity of...
Capacitors can be charged and discharged through a resistor. Meters with a data logger can be used to plot a graph of charge, p.d. or current against time. When a capacitor charges: Electrons flow onto the plate connected to the negative terminal of the power supply...
Capacitors store small amounts of energy that can be accessed quickly. The energy stored by a capacitor is equal to the work done by the battery. This is given by the area under a p.d.-charge graph. Capacitors are found in electronic devices that don’t need to store...
Capacitors are electrical components that can store charge. They consist of two conducting plates separated by a dielectric. When connected to a power source, positive and negative charge build up on opposite plates by removal and addition of electrons. The insulating...