G485 Flashcards
What is the absorption spectra of a gas?
A spectrum of dark lines across a pattern of spectral colours produced when light passes through a gas and the gas absorbs certain frequencies.
What is acoustic impedance (Z)?
The property of a metal which determines the intensity of ultrasound refracted at a boundary with another material.
What is radioactive activity?
The number of radioactive decays per unit time. Measured in becquerels (Bq)
What is an alpha particle?
A particle comprising of two protons and two neutrons ejected from the nucleus during radioactive decay
What is the amount of a substance?
An SI quantity, measured in moles
What is annihilation?
The process where a particle and antiparticle interact and their combined mass is converted into energy using E=mc^2
What is an antiparticle?
A particle of antimatter that has the same rest mass but, if charged, equal and opposite charge to its corresponding particle, e.g the positron is the antiparticle to an electron
What is an astronomical unit?
The average distance from the earth to the sun.
1 AU = 1.496x10^11m
What is the attenuation coefficient?
A constant used to calculate the intensity of X-Rays as they pass through a material.
What is a baryon?
A particle consisting of three quarks (e.g a proton or neutron)
What is the baryon number?
A property of baryons and quarks that is preserved in particle interactions
What is a becquerel?
A unit of activity, one becquerel is 1 radioactive decay per second.
What is beta decay?
When a neutron breaks down into a proton under the influence of the weak nuclear force it emits a beta particle and an antineutrino
What is a beta particle?
A high speed electron emitted from the nucleus during beta decay
What is the Big Bang theory?
The theory that the universe was created from nothing from a single point.
The universe was much hotter, smaller and denser. Then it expanded.
What are binary stars?
Two stars in orbit around their common centre of gravity.
What is the binding energy per nucleon?
The average energy required to remove a nucleon from the nucleus.
What is a black hole?
The remnants of the core of a very large star after it has gone supernova. It has infinite density and a gravitational field so great that even light can’t escape.
What is the Boltzmann constant? (k)
A constant used when dealing with gases relating the temperature of the gas to the average kinetic energy of the particles in the gas.
It can be thought of as the gas constant for a single molecule.
k=1.3807x10^-23 JK-1
What is a ‘bottom’?
A type of quark.
State Boyle’s Law
The volume of a fixed mass of gas is inversely proportional to the pressure exerted on it provided temperature remains constant.
What is Brownian motion?
The random movement of small particles when suspended in a liquid or gas.
What is Capacitance (c)
The charge stored per potential difference as given by C=Q/V.
Measured in Farads, F.
What is a capacitor?
An electrical component designed to store charge.
What is capacitor discharge?
Connection a charged dalai for across a resistor and so enabling the charge to flow from one plate to another.
The charge remaining decays exponentially.
What is the centripetal force?
The resultant force on an object acting towards the centre of the circle which is causing it to move in a circular path
What is a chain reaction?
One reaction causing another, which causes another etc.
E.g a nuclear chain reaction in a nuclear reactor or nuclear weapon.
What is a ‘charm’?
A type of quark.
What is the closed universe theory?
The idea that if the mean density of the universe is greater than the critical density, the universe will collapse back into a single point (I.e the Big Crunch)
What is a cloud chamber?
A device used to detect a charged particle by the formation of small clouds along trails of ions
What is collimation?
Focussing an electromagnetic wave (e.g X-Rays) to provide a parallel beam.
What is an AC Generator?
A generator that via the use of slip rings, produces an alternating emf and therefore an alternating current
What is a comet?
A body comprising mainly of ice and rock in an orbit around a star.
These orbits are usually highly elliptical
What is the Compton Effect?
The effect where X-Rays deflected off particles have a longer wavelength than their initial wavelength
What is Computerised Axial Tomography? (CAT)
A process using X-Rays in 3D and computers on order to produce and image of a slice through the body
What is conservation of charge?
A physical law which states that charge can not be created or destroyed, it is conserved in all interactions.
What is conservation of energy?
A physical law which states that in a closed system, energy can not be created or destroyed, just transformed from one state to another.
What is conservation of momentum?
The physical law which states that in the absence of external forces the total momentum for a system remains the same
What is the cosmological principle?
On a large scale, the universe is uniform. (is the same in every direction and of uniform density)
What is the Coulomb?
The unit of electrical charge. (C).
1C=1Ax1s
State Coulomb’s Law
The force between two charges is proportional to the product of their charges and inversely proportional to the square of the distance between the charges..
What is the Critical Density of the Universe?
The average density of the universe above which the universe will collapse (closed universe) and below which, the universe will continue expanding forever (open universe).
We think it is about 9.5x10^-27 kgm-3
What is the de Broglie equation?
An equation expressing the wavelength of a particle as a ratio of Planck’s constant and the particles momentum (mv)
What is the decay constant?
The probability of radioactive decay. =A/N, and measured in seconds.
What is the Doppler effect?
The change in wavelenth caused by the relative motion between the wave source and the observer
What is a ‘down’?
A type of quark.
What is Einstein’s mass/energy equation?
E=mc^2
What is electric charge?
Q=It, measured in Coulombs (C), a scalar quantity,
Charge = current x time
What is electric current?
A flow of Charge. A vector quantity measured in amperes (A)
What is electric field?
A region of space where a charged particle experiences a force. It goes from + to -.
What is electric field strength? (E)
The force per unit positive charge given by E = F/q
Measured in NC-1
What is electromagnetic induction?
The process of inducing an e.m.f. using a magnetic field and a changing flux linkage.
What is an electromagnetic wave?
A self propagating transverse wave that does not require a medium to travel through.
What is the Electromotive Force? (EMF)
The electrical energy transferred per unit charge when one form of energy is converted into electrical energy.
Measured in Volts.
What is an Electron?
A negatively charged sub-atomic particle with a charge of 1.6x10^-19 C.
Conduction electrons travel around circuits creating and electric current.
A lepton.
What is electron diffraction?
The process of diffracting an electron through a gap (usually between atoms of a crystal structure like graphite).
An example of wave particle duality.
What is the electronvolt?
One electronvolt is the energy change of an electron when it moves through a potential difference of one volt. Its value is 1.6x10^-19 J.
What is an endoscope?
A coated bundle of optic fibres inserted into the body to provide an image of the internal organs without a need for invasive surgery.
What is Energy? (E)
The stored ability to do work, measured in Joules (J).
A scalar quantity.
What are the energy levels of an electron?
The specific energies that an electron can have when it is in an atom which determine which shell it is in.
What is exponential decay?
At any given time interval there is the same ratio of final value to starting value. E.g capacitor discharge or radioactive decay
What is the Farad?
One farad is 1 coulomb stored per volt.
What is Faraday’s Law?
The magnitude of the induced emf is equal to the rate of change of flux linkage.
What is a field?
The region in which a force operates.
What is fission?
The process of splitting a large nucleus into two smaller nuclides, often with the emission of several neutrons. This releases energy because of the change in binding energy.
What are fission products?
The particles and energy released when a nucleus undergoes fission.
What is the flat universe theory?
The situation if the mean density of the universe is equal to the critical density. The galaxies in the universe will slow down, but never quite stop expanding.
