A-level Physics₇₄₀₈

Oscillation of the particles of the medium;

amplitude, frequency, wavelength, speed, phase, phase difference, $\mathit{c}\mathsf{=}\mathit{f}\mathit{\lambda }\mathit{ }\mathit{ }\mathit{ }\mathit{ }\mathit{ }\mathit{f}\mathsf{=}\frac{\mathsf{1}}{\mathit{T}}$

Phase difference may be measured as angles (radians and degrees) or as fractions of a cycle.

PS 2.3 / MS 0.1, 4.7 / AT a, b

Laboratory experiment to determine the speed of sound in free air using direct timing or standing waves with a graphical analysis.

Nature of longitudinal and transverse waves.

Examples to include: sound, electromagnetic waves, and waves on a string.

Students will be expected to know the direction of displacement of particles/fields relative to the direction of energy propagation and that all electromagnetic waves travel at the same speed in a vacuum.

Polarisation as evidence for the nature of transverse waves.

Applications of polarisers to include Polaroid material and the alignment of aerials for transmission and reception.

Malus’s law will not be expected.

PS 2.2, 2.4 / MS 1.2, 3.2, 3.4, 3.5 / AT i

Students can investigate the factors that determine the speed of a water wave.

Stationary waves.

Nodes and antinodes on strings.

$\mathit{f}\mathsf{=}\frac{\mathsf{1}}{\mathsf{2}\mathit{l}}\sqrt{\frac{\mathit{T}}{\mathit{\mu }}}$ for first harmonic.

The formation of stationary waves by two waves of the same frequency travelling in opposite directions.

A graphical explanation of formation of stationary waves will be expected.

Stationary waves formed on a string and those produced with microwaves and sound waves should be considered.

Stationary waves on strings will be described in terms of harmonics. The terms fundamental (for first harmonic) and overtone will not be used.

MS 4.7 / PS 1.2, 2.1 / AT i

Students can investigate the factors that determine the frequency of stationary wave patterns of a stretched string.

Required practical 1: Investigation into the variation of the frequency of stationary waves on a string with length, tension and mass per unit length of the string.

Path difference. Coherence.

Interference and diffraction using a laser as a source of monochromatic light.

Young’s double-slit experiment: the use of two coherent sources or the use of a single source with double slits to produce an interference pattern.

Fringe spacing, $\mathit{w}\mathsf{=}\frac{\mathit{\lambda }\mathit{D}}{\mathit{s}}$

Production of interference pattern using white light.

Students are expected to show awareness of safety issues associated with using lasers.

Students will not be required to describe how a laser works.

Students will be expected to describe and explain interference produced with sound and electromagnetic waves.

Appreciation of how knowledge and understanding of nature of electromagnetic radiation has changed over time.

AT i

Investigation of two-source interference with sound, light and microwave radiation.

Required practical 2: Investigation of interference effects to include the Young’s slit experiment and interference by a diffraction grating.

Appearance of the diffraction pattern from a single slit using monochromatic and white light.

Qualitative treatment of the variation of the width of the central diffraction maximum with wavelength and slit width. The graph of intensity against angular separation is not required.

Plane transmission diffraction grating at normal incidence.

Derivation of $\mathit{d}\sin \mathit{\theta }\mathsf{=}\mathit{n}\mathit{\lambda }$

Use of the spectrometer will not be tested.

Applications of diffraction gratings.

Refractive index of a substance, $\mathit{ }\mathit{n}\mathsf{=}\frac{\mathit{c}}{{\mathit{c}}_{\mathrm{s}}}$

Students should recall that the refractive index of air is approximately 1.

Snell’s law of refraction for a boundary ${\mathit{ }\mathit{ }\mathit{n}}_{\mathsf{1}}\sin \mathsf{}{\mathit{\theta }}_{\mathsf{1}}\mathsf{=}{\mathit{n}}_{\mathsf{2}}\sin \mathsf{}{\mathit{\theta }}_{\mathsf{2}}$

Total internal reflection $\sin \mathsf{}{\mathit{\theta }}_{\mathrm{c}}\mathsf{=}\frac{{\mathit{n}}_{\mathsf{2}}}{{\mathit{n}}_{\mathsf{1}}}$

Simple treatment of fibre optics including the function of the cladding.

Optical fibres will be limited to step index only.

Material and modal dispersion.

Students are expected to understand the principles and consequences of pulse broadening and absorption.

MS 0.6, 4.1