2.1 Properties of Waves

• Rectilinear propagation, reflection, refraction, diffraction and interference (qualitative treatment)
• Stationary waves and their applications; resonance
• Applications of wave properties; the need for modulation
• Production and detection of frequency-modulated waves
• The Doppler effect and its applications

• explain wave properties in real life situations
• demonstrate the properties of waves
• demonstrate the formation and properties of stationary waves in nature
• describe applications of stationary waves
• describe the Doppler effect and its applications in day-to-day life
• appreciate the formation and application of waves in real life situations

“Why can you hear someone round a corner but not see them?”

“Why does an ambulance siren change pitch as it passes you?”

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1. How waves behave
   40 min · 2 practice tasks · quiz
   Five things every wave does, and why you can hear round a corner but not see round one.
2. Stationary waves and resonance
   40 min · 2 practice tasks · quiz
   Waves that go nowhere, the points that never move, and why a bridge can be shaken apart by a small push.
3. The Doppler effect and sending signals
   40 min · 2 practice tasks · quiz
   Why a passing siren changes pitch, and why radio stations do not simply broadcast sound.
4. Transverse waves
   40 min · 1 practice tasks · quiz
   Particles that oscillate at right angles to the energy, from a shaken kamba to light and radio.
5. Longitudinal waves
   40 min · 1 practice tasks · quiz
   Compressions and rarefactions on a slinky, and why a shout is a push-pull of air, not a crest.
6. Comparing transverse and longitudinal waves
   40 min · 1 practice tasks · quiz
   One table that sorts rope, sound, light and water, and the polarisation test that settles arguments.
7. Amplitude and energy
   40 min · 1 practice tasks · quiz
   Rest-to-crest, not crest-to-trough, and why a louder matatu horn is a bigger push of the same note.
8. Wavelength and period
   40 min · 1 practice tasks · quiz
   From crest to crest, from compression to compression, and the time T for one full cycle.
9. Frequency and the hertz
   40 min · 1 practice tasks · quiz
   How many waves per second, from a 50 Hz mains hum to a 100 MHz FM station in Nairobi.
10. The wave equation v = fλ
    40 min · 1 practice tasks · quiz
    Rearranging v = fλ, keeping the units honest, and why slower water has to have a shorter wavelength.
11. Measuring the speed of a wave
    40 min · 1 practice tasks · quiz
    Timing a pulse on a rope, using v = d/t, checking with v = fλ, and the thunder-after-lightning estimate.
12. Rectilinear propagation
    40 min · 1 practice tasks · quiz
    Waves travel in straight lines in a uniform medium, which is why a jacaranda casts a sharp shadow.
13. Reflection of waves
    40 min · 1 practice tasks · quiz
    The law i = r for ripples, echoes and mirrors, with speed, frequency and wavelength unchanged.
14. Refraction of waves
    40 min · 1 practice tasks · quiz
    Waves change speed at a boundary, frequency stays, wavelength follows, and the wavefronts swing.
15. Diffraction of waves
    40 min · 1 practice tasks · quiz
    Spreading at a gap or edge, greatest when the gap is about one wavelength — the doorway, properly.
16. Interference of waves
    40 min · 1 practice tasks · quiz
    Displacements add: loud and quiet, bright and dark, from two coherent sources.
17. Water waves in a ripple tank
    40 min · 1 practice tasks · quiz
    How to set up the tank so reflection, refraction, diffraction and interference are not just stories.
18. Sound as a wave
    40 min · 1 practice tasks · quiz
    A longitudinal wave that needs a medium, travels at about 340 m/s in air, and travels faster in water and steel.
19. Echoes, sonar and ultrasound
    40 min · 1 practice tasks · quiz
    The two-way trip 2d = vt, from a clap in a hall to a Lake Victoria echo sounder and a KNH scan.
20. Pitch, loudness and quality
    40 min · 1 practice tasks · quiz
    Three ways a note can differ: frequency, amplitude, and the mix of harmonics that makes a nyatiti unlike a guitar.
21. Investigating stationary waves
    40 min · 1 practice tasks · quiz
    Find nodes on a string, count loops, and get λ and v from a sonometer or a guitar.
22. The resonance tube and the speed of sound
    40 min · 1 practice tasks · quiz
    A closed air column, L = λ/4 at the first loud point, and v = 4 f L from a fork and a measuring cylinder.
23. Producing and detecting FM waves
    40 min · 1 practice tasks · quiz
    From microphone to Kiss FM mast and back: carrier, frequency modulation, resonance tuning and demodulation.
24. Waves around Kenya
    40 min · 1 practice tasks · quiz
    One country using reflection, refraction, diffraction, interference, resonance and the Doppler effect in real jobs.