C2 Wave Model

Wave Model

C2.1 Travelling wave

Oscillations that transfer energy from 1 place to another without transferring matter.

Travel through medium or in vacuum

C2.2 Terms waves (x, λ, A, T, f)

displacement x from equilibrium position.
wavelegth λ length of one complete oscillation (measure 2 crests, 2 troughs)
amplitude A max displacement from x=0
period T time take for 1 complete oscillation
frequency f nr of complete oscillations (passing fixed point) per second f = ¹/_T

C2.3 Wave equation (speed)

distance travelled by wave per second: v = fλ = λ/T
f ∝ ¹/λ

C2.4 Transverse waves

A wave oscillating perpendicular to direction of energy transfer: each particle moves up and down, or side to side. Peaks and troughs. Eg. EM waves, vibrations on guitar string, ripple tank.
Can travel through vacuum.

Wavefront diagram: mid source of oscillations with circles around it, λ away from each other. Ray diagram: perp to wavefront rays in directiom of energy flow.

C2.5 Longitudinal waves

A wave oscillating parallel to direction of energy transfer. particles vibrate back and forth.
Rarefaction: low pressure, particles far apart
Compression: high pressure, particles close tg
oscillates left right.
eg. sound waves.
need particles to propegate; not through vacuum; dont hear anything in vacuum (space)

C2.6 Sound waves

Longitudinal, need medium.
Generated by oscillating sources; change in density of surrounding medium; make compressions and rarefactions. All animals have audible range of frequencies they can hear, elephants (low f), humans (mid), bats (high f)

C2.7 Pitch, volume, speed of sound

Pitch = frequencies: high pitch=high f (short λ) , low pitch=low f (long λ)
Volume = amplitudes: large A;highV, smallA;lowV
Speed of sound; constantish, 340 ms^-1 in air at room T (higher T, greater V, partic higher E_k)

Sound travels fastest through solids (closely packs part), slowest in gases (spread, less effic)

C2.8 EM spectrum

1. Combined electric and magnetic field.

2. Fields oscillate perpendicularly to each other in direction of wave. eg. E_field on y axis, M_field on z axis, wave moves on x axis.

3. Transverse waves: all have v = c = 3×10⁸ ms^-1 (speed of light)

4. Continuous spectrum based on f. Shorter λ, higher f, greater Energy

5. Humans see 400nm<λ<700nm; visible spectrum.

6. c = fλ

7. No medium required

8. Oscillating charged particles