1. Waves

2. A wave is any disturbance that transmits energy through matter or space Imagine that you just came home from a day at the beach, you had fun, but you’re hungry so you put some leftover pizza in the microwave and listen to the radio while you wait. Your phone rings and it’s your best friend calling to find out if you’ve done science HW yet. Name some waves in the paragraph above. How many different waves were present?

3. Waves carry energy Energy can be carried away from its source by a wave, but the material through which a wave travels does not move with the energy. Ex: wave in a tidal pool As a wave travels, it uses energy to do work on everything in its path

4. Energy transfer A medium is a substance through which a wave can travel. It can be a solid, liquid, or gas. Some waves transfer energy by the vibration of particles in a medium. Sound waves need a medium. If there are no particles to vibrate, there will be no sound (vacuum). Ex: tuning fork

5. Types of waves Mechanical waves: waves that need a medium. Ex: seismic waves of earthquakes Electromagnetic waves: waves that do not need a medium and can travel through substances. They travel the fastest through empty space. Ex: visible light

6. Types of waves Transverse wave (“moving across”): particles vibrate in an up and down motion at right angles to the direction the wave travels. Ex: waves on a rope Longitudinal wave: particles of the medium vibrate back and forth in the direction the wave travels. Ex: a spring. Ex: sound waves from hitting a drum Compression = when particles are crowded together Rarefaction = when particles are less crowded than normal

7. Types of waves Surface wave: combination of transverse and longitudinal waves at the boundary between two media

8. Wave speed The speed at which a wave travels Depends on the medium Can be calculated using wavelength and frequency: v = λ x f v = speed λ= wavelength f = frequency

9. Wave speed calculations The frequency of a wave is 3/s or 3 Hz. The wavelength is 0.5 m. What is the wave speed? The frequency of a wave is 2/s or 2 Hz. The wavelength is 1.5 m. What is the wave speed?

10. Wave calculations The speed of a wave is 20 m/s and it has a frequency of 4 Hz. What is the wavelength? The speed of a wave is 15 m/s and it has a frequency of 2 Hz. What is the wavelength?

11. Wave calculations A wave has a speed of 20 m/s and a wavelength of 2.5 m. What is the frequency? A wave has a speed of 10 m/s and a wavelength of 2 m. What is the frequency?