Key areas Maxima and minima are produced when the path difference between waves is a whole number of wavelengths or an odd number of half wavelengths respectively. Carry out calculations on the above.

What we will do today: Identify interference patters for both maxima and minima. Carry out calculations on the above.

Interference Patterns

Maxima In an interference pattern formed by two coherent sources, maxima occur at points of constructive interference: Path difference = nλ for maxima where n is an integer, λ is the wavelength i.e. path difference = λ, 2λ, 3λ, etc. Note - the space between each maxima is equal to one wavelength.

Minima Minima occur at points of destructive interference: Path difference = (n+½)λ for minima i.e. path difference = ½λ, 1½λ, 2½λ, etc.

Example Find the wavelength of the waves used below if the second off-centre maximum occurs at A: Path difference = 36 – 24 = 12cm; n = 2 For maxima: path difference = n λ λ = path difference / n = 12 / 2 = 6cm

Old Higher Past Paper Questions Multi-Ch: 2000 – 14 2001 – 15 2004 – 14 2008 – 14 Section B 2003 – 28 2010 - 27

2000 – Qu: 14

2001 – Qu: 15

2004 – Qu: 14

2008 – Qu: 14

2012 – Qu: 9

2013 – Qu: 28(a)

2014 – Qu: 28(b)

Questions Class jotter Qu’s: 6 - 8