PHYA2 Waves Revision Notes

Just a few revision notes relevant to the AQA PHYA2 Waves Specification.

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  • Created on: 24-05-14 18:50
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AQA AS Physics A
PHYA2 ­ Mechanics, Materials and Waves
Revision Notes - Waves
The frequency of a wave is the number of cycles that occur in one second. The unit of frequency is the
Hertz, Hz. A frequency of 1Hz is one wave per second.
KHz = Kilohertz = 103
MHz = Megahertz = 106
GHz = Gigahertz = 109
THz = Terahertz = 1012
Wavelength Equation
= c
f
c = Speed of light in a vacuum
f = frequency
Re-arrangement:
c = f
f = c
Velocity of a wave
v = f
V = velocity of the wave
= wavelength
f = frequency
The change of direction when a wave moves from one medium to another is called refraction.
Refractive Index:
c
n = cs
n = Refractive index
c = Speed of light in a vacuum
cs = Speed of light in the material/medium
Re-arrangement:
c = n × cs
c
cs = n

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AQA AS Physics A
PHYA2 ­ Mechanics, Materials and Waves
Revision Notes - Waves
Critical angle equation:
n
sin c = n21 Where n2 < n1
c = Critical angle
n1 = Refractive index 1
n2 = Refractive index 2
Re-arrangement:
n
c = sin-1 n21
n
n1 = sin 2
c
n2 = sin c × n1
Superposition of waves ­ Stationary waves
When two similar waves meet, the resultant wave depends on the amplitude and relative phase of
the two waves.…read more

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AQA AS Physics A
PHYA2 ­ Mechanics, Materials and Waves
Revision Notes - Waves
The distance between the two slits, d. increasing d makes the interference fringes closer
together.
The wavelength of light, . The fringes are closer together at short wavelengths.
The distance, D, between the slits and the screen. If we observer the interference pattern
further away from the slits, the fringes are further apart.…read more

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AQA AS Physics A
PHYA2 ­ Mechanics, Materials and Waves
Revision Notes - Waves
n
d = sin
n = dsin
= dsin
n
The first maximum will occur when n = 0, i.e. when the light from adjacent slits has zero path
difference. This will happen when = 0° . This is the `straight through position' referred to as the
zero order maximum.…read more

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AQA AS Physics A
PHYA2 ­ Mechanics, Materials and Waves
Revision Notes - Waves
Diffraction gratings are useful for analysing the light from stars, enabling astronomers to determine
what elements are present, what the surface temperature of the star is moving.…read more

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