Unit 2: Waves and Electricity

Understand the terms amplitude, frequency, period, speed and wavelength

Be able to use the wave equation v = fλ

Be able to describe longitudinal waves in terms of pressure variation and the displacement of molecules

Be able to describe transverse waves

Be able to draw and interpret graphs representing transverse and longitudinal waves including standing/stationary waves

CORE PRACTICAL 4: Determine the speed of sound in air using a 2-beam oscilloscope, signal generator, speaker and microphone

Know and understand what is meant by wavefront, coherence, path difference, superposition, interference and phase

Be able to use the relationship between phase difference and path difference

Know what is meant by a standing or stationary wave, understand how it is formed, and identify nodes and antinodes.

Use v = √(T/μ) for the speed of a transverse wave on a string.

CORE PRACTICAL 5: Investigate how length, tension and mass per unit length affect the frequency of a vibrating string or wire.

Use I = P/A for the intensity of radiation.

Use n1 sin θ1 = n2 sin θ2 at a boundary between two media and refractive index n = c/v.

Calculate critical angle using sin C = 1/n.

Be able to predict whether total internal reflection will occur at an interface

Understand how to measure the refractive index of a solid material

Understand what is meant by plane polarisation

Understand what is meant by diffraction and use Huygens’ construction to explain what happens to a wave when it meets a slit or an obstacle

Be able to use nλ = dsinθ for a diffraction grating

CORE PRACTICAL 6: Determine the wavelength of light from a laser or other light source using a diffraction grating

Understand how diffraction experiments provide evidence for the wave nature of electrons

Use the de Broglie equation λ = h/p.

Understand that waves can be transmitted and reflected at an interface between media

Understand how a pulse-echo technique can provide information about the position of an object and how the amount of information obtained may be limited by the wavelength of the radiation or by the duration of pulses

Understand how the behaviour of electromagnetic radiation can be described in terms of a wave model and a photon model, and how these models developed over time

Be able to use the equation E = hf, that relates the photon energy to the wave frequency

Understand that the absorption of a photon can result in the emission of a photoelectron

Understand threshold frequency and work function and use the photoelectric equation hf = φ + ½mvmax².

Be able to use the electronvolt (eV) to express small energies

Understand how the photoelectric effect provides evidence for the particle nature of electromagnetic radiation

Understand atomic line spectra in terms of transitions between discrete energy levels and understand how to calculate the frequency of radiation that could be emitted or absorbed in a transition between energy levels.

2.4.64Electric current

Understand current as the rate of flow of charge and use I = ΔQ/Δt.

2.4.65Potential difference

Use potential difference V = W/Q.

2.4.66Resistance and Ohm’s law

Understand resistance R = V/I and Ohm's law as the special case I ∝ V at constant temperature.

2.4.67Current and p.d. distributions in circuits

(a) understand how the distribution of current in a circuit is a consequence of charge conservation (b) understand how the distribution of potential differences in a circuit is a consequence of energy conservation

2.4.68Combining resistances in series and parallel

Be able to derive the equations for combining resistances in series and parallel using the principles of charge and energy conservation, and be able to use these equations

2.4.69Electrical power and energy

Use P = VI and W = VIt, and derive and use P = I²R and P = V²/R.

2.4.70I-V graphs for circuit components

Sketch, recognise and interpret current–potential-difference graphs for ohmic conductors, filament bulbs, thermistors and diodes.

2.4.71Resistivity

Use R = ρl/A for the resistance of a uniform conductor.

2.4.72Core Practical 7 - electrical resistivity

CORE PRACTICAL 7: Determine the electrical resistivity of a material

2.4.73Conduction model and resistivity

Be able to use I = nqvA to explain the large range of resistivities of different materials

2.4.74Potential along a current-carrying wire

Understand how the potential along a uniform current-carrying wire varies with the distance along it

2.4.75Potential divider circuits

Understand the principles of a potential divider circuit and understand how to calculate potential differences and resistances in such a circuit

2.4.76Variable-resistance potential dividers

Be able to analyse potential divider circuits where one resistance is variable including thermistors and light dependent resistors (LDRs)

2.4.77E.m.f. and internal resistance

Know the definition of electromotive force (e.m.f.) and understand what is meant by internal resistance and know how to distinguish between e.m.f. and terminal potential difference

2.4.78Core Practical 8 - e.m.f. and internal resistance

CORE PRACTICAL 8: Determine the e.m.f. and internal resistance of an electrical cell

2.4.79Temperature effects on resistance

Understand how changes of resistance with temperature may be modelled in terms of lattice vibrations and number of conduction electrons and understand how to apply this model to metallic conductors and negative temperature coefficient thermistors

2.4.80Illumination effects on LDR resistance

Understand how changes of resistance with illumination may be modelled in terms of the number of conduction electrons and understand how to apply this model to LDRs.