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Published byGwen Peters Modified over 4 years ago

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**Vocabulary Review Properties of Waves The Electromagnetic Spectrum**

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**Vocabulary Review Progressive waves Describing wave motion**

Displacement Amplitude Wavelength Period Frequency Speed

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**Intensity Energy passing through a unit area in unit time.**

Intensity ~ Square of the amplitude I ~ A2 Intensity ~ 1/d2 Where d is distance from source

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Example 1 A health inspector is measuring the intensity of a sound. Near a loudspeaker his meter records an intensity I. This corresponds to an amplitude A of the sound wave. At another position the meter gives an intensity reading of 2 I. What is the corresponding sound wave amplitude?

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Example 2 The intensity I of a sound at a point P is inversely proportional to the square of the distance x of P from the source of the sound. Air molecules at P, a distance r from S, oscillate with amplitude 8.0 μm. Point Q is situated a distance 2r from S. What is the amplitude of oscillation of air molecules at Q?

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Phase The corresponding angular displacement relative to a complete wave of a point on the wave

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Phase 0⁰ 180⁰ or п

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Phase 90⁰ or п/2 270⁰ or 3п/2

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Phase Difference The difference in angles between two waves at a specific point.

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Phase Difference Phase difference of п at all points

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Phase Difference Phase difference of п at all points

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Coherence When two waves have constant phase difference, then they are coherent. Coherence occurs when two waves have the same frequency or period.

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Non-Coherence

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In Phase Phase difference is a multiple of 2п at all points.

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Out of Phase Phase difference is not a multiple of 2п.

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Out of Phase Phase difference of п at all points

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**Wave Properties For all waves Reflection Refraction Diffraction**

Bouncing of waves off a surface Refraction Change of wave speed as it passes from one medium to another (from one depth to another) Bending of waves Diffraction Bending of waves around a barrier

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**Wave Properties Question**

Which wave properties change when light passes from air into glass? A colour and speed B frequency and wavelength C speed and wavelength D wavelength and colour

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**Polarisation Oscillation that takes place in one direction.**

Only true for transverse waves.

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Polarisation

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**The Electromagnetic Spectrum**

Electromagnetic waves are transverse waves They are non-mechanical waves Do not require a medium to transfer energy Travel at the same speed in a vacuum 3 x 10 8 ms-1

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**Orders of Magnitude (Wavelength)**

Gamma Rays X-Rays Ultraviolet Rays Visible Light ROY G BIV m 10-10 m 10-7 m 10-7m (700 nm -400 nm)

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**Orders of Magnitude (Wavelength)**

Infrared Microwaves Radio Waves 10 -6 m 10-2 m 10 2 m

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