4.4 Waves
4.4.1 Wave Motion
Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) progressive waves; longitudinal and transverse waves
(b) (i) displacement, amplitude, wavelength, period, phase difference, frequency and speed of a wave
(ii) techniques and procedures used to use an oscilloscope to determine frequency
You don't need any details like sweep rates or which knob is which, just that the x-axis is time, so to get frequency you need to use the equation below.
(c) the equation
(d) the wave equation
(e) graphical representations of transverse and longitudinal waves
(f) (i) reflection, refraction, polarisation and diffraction of all waves
Learners will be expected to know that diffraction effects become significant when the wavelength is comparable to the gap width.
Just like at GCSE, this is still the answer to any diffraction question.
(ii) techniques and procedures used to demonstrate wave effects using a ripple tank
(iii) techniques and procedures used to observe polarising effects using microwaves and light
(g) intensity of a progressive wave;
4.4.2 Electromagnetic Waves
Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) electromagnetic spectrum; properties of electromagnetic waves
(b) orders of magnitude of wavelengths of the principal radiations from radio waves to gamma rays
This means that you have to learn the wavelengths. There is no way round it. They do ask!
(c) plane polarised waves; polarisation of electromagnetic waves
Learners will be expected to know about polarising filters for light and metal grilles for microwaves in demonstrating polarisation.
(d) (i) refraction of light; refractive index; n sin θ = constant
(ii) techniques and procedures used to investigate refraction and total internal reflection of light using ray boxes, including transparent rectangular and semi-circular blocks
(e) critical angle; ; total internal reflection for light.
4.4.3 Superposition
Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) (i) the principle of superposition of waves
(ii) techniques and procedures used for superposition experiments using sound, light and microwaves
(b) graphical methods to illustrate the principle of superposition
(c) interference, coherence, path difference and phase difference
(d) constructive interference and destructive interference in terms of path difference and phase difference
The key here is to be either talking about path difference OR phase difference. You should never use them both in the same sentence.
(e) two-source interference with sound and microwaves
(f) Young double-slit experiment using visible light
Learners should understand that this experiment gave a classical confirmation of the wave-nature of light.
This is the experiment that proves that light is a wave because only waves could interfere in this way. In the next section you will learn about the photo-electric effect that is the experiment that proves that light is a particle!
(g) (i) for all waves where a << D
(ii) techniques and procedures used to determine the wavelength of light using (1) a double-slit, and (2) a diffraction grating.
The diffraction grating comes back in the A2 spec when we talk about stars. We will visit it briefly at this point, but will cover it more fully later.
4.4.4 Standing Waves
Learners should be able to demonstrate and apply their knowledge and understanding of:
(a) stationary (standing) waves using microwaves, stretched strings and air columns
(b) graphical representations of a stationary wave
(c) similarities and the differences between stationary and progressive waves
(d) nodes and antinodes
the nodes are where there is no vibration (no for nodes)
(e) (i) stationary wave patterns for a stretched string and air columns in closed and open tubes
(ii) techniques and procedures used to determine the speed of sound in air by formation of stationary waves in a resonance tube
(f) the idea that the separation between adjacent nodes (or antinodes) is equal to wavelength/2 it is the wavelength of the progressive wave
(g) fundamental mode of vibration (1st harmonic); harmonics.