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Waves equations

The 22 equations the waves notes display, each with a link to the lesson that states it. Of the 22, the data booklet prints 8, 5 are yours to memorise and 9 carry no badge either way.

Year 12 · 9 lessons with equations.

The marks refer to the AQA 7408 data booklet. An equation it prints is marked as such, and one it leaves out is marked to learn. An equation with no mark has not been checked against that booklet, and some of these belong to the Edexcel, OCR or CIE specification rather than AQA’s, so check them against your own board’s data or formula booklet.

9 lessons

Progressive waves

f = \frac{1}{T}

IN THE AQA DATA BOOKLET

c = f\lambda

IN THE AQA DATA BOOKLET

\text{phase difference} = \frac{2\pi d}{\lambda}

NOT IN THE AQA DATA BOOKLET: LEARN IT

Polarisation and electromagnetic waves

I = I_0\cos^2\theta

Stationary waves on strings

\lambda_n = \frac{2L}{n}

NOT IN THE AQA DATA BOOKLET: LEARN IT

v = \sqrt{\frac{T}{\mu}}

f_1 = \frac{1}{2L}\sqrt{\frac{T}{\mu}}

IN THE AQA DATA BOOKLET

Stationary waves in air columns

\lambda_1 = 4L

Closed pipe, first harmonic: one end closed, end corrections neglected.

\lambda_n = \frac{4L}{n}

Closed pipe: odd harmonics only, n = 1, 3, 5, …

v = 2f(L_2 - L_1)

Refraction and Snell's law

n = \frac{c}{c_s}

IN THE AQA DATA BOOKLET

n_1 \sin\theta_1 = n_2 \sin\theta_2

IN THE AQA DATA BOOKLET

n = \frac{\sin\theta_1}{\sin\theta_2}

Total internal reflection and optical fibres

\sin\theta_c = \frac{n_2}{n_1}

IN THE AQA DATA BOOKLET

Interference and Young's double slit

\text{constructive: path difference} = n\lambda

NOT IN THE AQA DATA BOOKLET: LEARN IT

\text{destructive: path difference} = (n + \tfrac{1}{2})\lambda

NOT IN THE AQA DATA BOOKLET: LEARN IT

w = \frac{\lambda D}{s}

IN THE AQA DATA BOOKLET

Diffraction gratings

d \sin\theta = n\lambda

IN THE AQA DATA BOOKLET

d = \frac{1}{N}

NOT IN THE AQA DATA BOOKLET: LEARN IT

Lenses and images

Not on the AQA specification: Edexcel only.

P = \frac{1}{f}

\frac{1}{u} + \frac{1}{v} = \frac{1}{f}

m = \frac{v}{u}

Every equation in the library is indexed by unit on the equation index, and the waves notes are where these equations are derived and used. The 5 the booklet leaves out are on the equations to memorise, alongside the rest of the course.

Also: Materials equations · Quantum phenomena equations