1. Waves

2. Deep Impact video snippet Notice the ripple formed when the comet hits the ocean How do you think the energy of the impact reached the land and cause destruction of infrastructure? CLICK HERE

3. Waves transfer energy, not matter Ripple tank and Slinky demo

4. Physical characteristics of wave Wavelength – distance from one crest to the next crest or from one trough to the next trough Wavelength – distance from one crest to the next crest or from one trough to the next trough Amplitude – largest displacement of the particle in the medium from its equilibrium position (displacement = 0) Amplitude – largest displacement of the particle in the medium from its equilibrium position (displacement = 0) Equilibrium position crest trough

5. Physical characteristics of a wave Frequency ( f ) – The number of waves produced in 1second Frequency ( f ) – The number of waves produced in 1second Note: units for frequency is hertz or Hz Period (T) – The time taken to produce one complete wave (ie covers one wavelength) Period (T) – The time taken to produce one complete wave (ie covers one wavelength) f http://www.surendranath.org/Applets.html http://www.surendranath.org/Applets.html http://www.surendranath.org/Applets.html waves transverse waves waves transverse waves

6. Wave motion Motion of mechanical wave (as opposed to electromagnetic wave) due to vibration of particles in a medium Motion of mechanical wave (as opposed to electromagnetic wave) due to vibration of particles in a medium Transverse – vibration of particles perpendicular to direction of wave propagation (wave motion) Transverse – vibration of particles perpendicular to direction of wave propagation (wave motion) Longitudinal – vibration of particles parallel to direction of wave propagation (wave motion) Longitudinal – vibration of particles parallel to direction of wave propagation (wave motion) http://www.cbu.edu/~jvarrian/applets/waves1/lontra_g. htm http://www.cbu.edu/~jvarrian/applets/waves1/lontra_g. htm http://www.cbu.edu/~jvarrian/applets/waves1/lontra_g. htm http://www.cbu.edu/~jvarrian/applets/waves1/lontra_g. htm Note that a medium is required before a mechanical wave can propagate! Note that a medium is required before a mechanical wave can propagate!

7. Longitudinal vs Transverse waves Slinky demonstration

8. Let’s do the Kallang Wave!

9. Speed of waves Recall speed = So for waves, speed v = distance covered in 1 wavelength time taken to cover 1 wavelength Recall f so speed of waves v = Speed equation for waves v = f Note that speed of waves  speed of vibration of particles in medium http://www.surendranath.org/Applets.html

10. Ripples in water http://www.falstad.com/ripple/

11. Let’s play with the Slinky!

12. Worksheet on Stadium Wave A stadium wave typically has a wavelength of 5m. If the speed of the wave that moves round the stadium is 20m/s. Imagine you are one of the spectators in the crowd. How many waves do you expect to see being generated per second? f = v/ So f = 20/5 = 4 Hz 4 waves are generated per second How long does it take one wave to be generated? T = 1/ f So T = 1/4 = 0.25s Given that the total circumference of the stadium is 800m, how long do you have to wait before the next round of wave reaches you? time taken = distance/speed So wait time = 800/20 =40s

13. WAVES Properties Wavelength Amplitude Frequency f Wave equation v = f Period T Wave motion TransverseLongitudinal Examples Ripples in water Stadium wave Due to vibration of particles in medium Speed v Types of mechanical wave f = 1 / T More next lesson