A-level Waves and Ting G482 Flashcards
Define the Coulomb
The SI unit of electrical charge. 1 Coulomb of electrical charge is the amount of charge transferred by a current of 1Amp in 1 Second
Define potential difference (p.d.);
Electrical energy transfered per unit charge when electrical energy is converted to another form.
define the volt
1 Volt is equal to 1 Joule per Coulomb
define electromotive force (e.m.f.) of a source such as a cell or a power supply
The amount of energy per unit charge converted to electrical from other forms, usually in a cell or power supply.
(N.B. This is almost the exact opposite of P.D.)
Define resistance
Resistance, R, in any circuit (series, parallel, or any combination) is the opposition created to the flow of current, I, when a potential difference, V, is applied to the circuit.
This opposition to the flow of current is expressed in Ohm’s Law as R = V/I, where R is the resistance in ohms, V is the applied potential in volts, and I is the resulting current in amperes.
Define the ohm
1 Ohm is the resistance of a component when a potential difference of 1 volt is produced per ampere of current.
define resistivity of a material
The resistivity of a wire of length “l” resistance “R” and area of cross section “A” is given by p = RA/l
# define the kilowatt-hour (kW h) as a unit of energy
A unit of energy equal to 36 MJ or 1kW for 1h
define and use the terms displacement,
amplitude, wavelength, period, phase
difference, frequency and speed of a wave
Displacement-Distance from the mean position expressed as a vector
Amplitude- Maximum displacement
Wavelength-Distance between neighbouring identical points
Period-Time taking for one complete oscillation of a particle
Phase Difference- The fraction of a cycle between the oscillations of two particles
Frequency-Number of waves passing a point per unit time
Speed-Distance travelled by the wave per unit time
define the terms nodes and antinodes
Node-Fixed point on a standing wave where the amplitude is always zero
Antinode-Fixed point along a standing wave where the amplitude of the oscillations will periodically be at a maximum.
define and use the terms fundamental mode of vibration and harmonics
Simplest pattern of movement and has the lowest possible frequency band and the longest wavelength
Harmonics are different modes of vibration of a wave with increasing frequency and decreasing wavelength

define and use the electronvolt (eV) as a unit of energy
1 eV is gained or lost when an electron moves through a potential difference of 1V
Energy acquired by an electron accelerated through a p.d of 1V.
1eV=1.6×10^(-19)J
define and use the terms work function and threshold frequency
Work function- the minimum energy required to release an electron from the surface of a material
Threshold frequency- Frequency of a photon that will just emit an electron from a substance without any kinetic energy
Define the term intensity
Intensity is the (incident) energy per unit area per second
state what is meant by the term mean drift
velocity of charge carriers
The average distance travelled by the charge carriers along the wire per second
state and use Ohm’s law
For a metallic conductor at constant temperature, the current in the conductor is directly proportional to the potential difference across it
state and use Ohm’s law
For a metallic conductor at constant temperature, the current in the conductor is directly proportional to the potential difference across it
state Kirchhoff’s second law and appreciate that this is a consequence of conservation of energy
Energy is conserved
Sum of e.m.f’s=sum of voltages (total of p.d’s in a loop)
state typical values for the wavelengths of the different regions of the electromagnetic
spectrum from radio waves to γ-rays
Visible 600-400nm (5 x 10-7)
UV-A 400-315nm
UV-B 315-260nm
UV-C 260-100nm
state three things that electromagnetic waves have in common
Travel at the same speed “c” in a vacuum
All transfer both Energy and Information
All are transverse (travel at 90 degrees to the direction of oscillation)
state why polarisers can be used to see deeper into water.
Light is partially polarised upon reflection.
State the principle of superposition of waves
When two waves meet at a point and interfere the sum of their individual dislacement is equal to the sum of the resultant displacement.
State what is meant by constructive/destructive interference
interference is when two or more waves interact/superpose and there is a change in overall intensity or displacement.
Constructive interference is where net displacement is larger than the displacement of the two original waves
Destructive interference is where the net displacement is smaller that one ( or all) of the original waves
What is a photon?
A photon is a quantum (discrete amount) of energy of electromagnetic radiation








