| What do Mechanical & Electromagnetic Waves Cause oscillations in? | - Mechanical waves: cause oscillations of particles in a solid, liquid or gas and must have a medium to travel through.
- Electromagnetic waves: cause oscillations in electrical and magnetic fields. |
| PRACTICAL: Ripple Tank (6 stages) | 1) Set up ripple tank with 5cm depth of water
2) Adjust height of the wooden rod so it just touches the surface of the water
3) Switch on lamp and motor & adjust until low frequency waves can be clearly observed
4) Measure length of a number of waves then divide by the number of waves to record wavelength. Or you can take a photograph of the card with the ruler and take measurements from the still picture
5) Count the number of waves passing a point in ten seconds then divide by ten to record frequency
6) Calculate speed of the waves using: wave speed = frequency × wavelength |
| PRACTICAL: Measuring waves in a Solid (5 stages) | 1) Attach a string or cord to a vibration generator and use a 200 gram (g) hanging mass and pulley to pull the string taut. Place a wooden bridge under the string near the pulley.
2) Switch on vibration generator and adjust the wooden bridge until stationary waves can be clearly observed
3) Measure the length of as many half wavelengths (loops) as possible, divide by the number of half wavelengths (loops) that you've measured. This is half the wavelength, doubling this gives the wavelength
4) The frequency is the frequency of the power supply
5) Calculate the speed of the waves using: wave speed = frequency × wavelength |
