Waves&sound
- 2. Waves are all around us! Water waves Sound waves Earthquake (seismic waves) Waves carry energy! Example: Electromagnetic waves.
- 3. What is a wave? A wave is a disturbance that travels through space and matter, accompanied by a transfer of energy. Example: the surface of a pond is actually calm until we drop a pebble. Then the surface of the water starts to move as it is disturbed. That disturbance spreads outwards.
- 4. Types Of Waves There are two types of waves: 1. Transverse waves 2. Longitudinal waves
- 5. The direction of vibration is perpendicular to the direction of wave travel. Example: water waves, electromagnetic waves
- 6. The direction of vibration is parallel to the direction of wave travel. Example: sound
- 7. Vocabulary Crests / trough The high points / low points in a wave Amplitude Maximum displacement from rest position Phase Two points that are moving in the same direction at the same speed and having the same displacement from rest Wavelength Shortest distance between two points Frequency Number of complete waves produced in 1 second Period/Cycle Time taken to produce 1 complete wave Wave speed Distance travelled by the wave in 1 second.
- 9. Sound is….. A form of energy an example of longitudinal wave Produced by vibrating sources placed in a medium. (solid, liquid or gas)
- 10. Any medium that has particles that can vibrate will transmit sound. Solids can transmit sound best , followed by liquid then air. Application: In olden days, people would hear the ground for movement.
- 11. Temperature? Sound travels faster in higher temperatures Humidity? Sound travels faster in high humidity Pressure? Pressure has no effect on speed of sound
- 12. The human ear can only hear sounds of frequencies between 20 Hz and 20 kHz. Any sound with frequency higher than 20 kHz is known as ultrasound. Any sound with frequency lower than 20 Hz is known as infrasound.
- 13. Ultrasound is used in medical diagnosis to obtain images of internal parts of the body. Commonly used in pre-natal examination.
- 14. Formation of Echoes When sound hits a hard surface, it will “bounce” off the surface. The sound that is reflected back to us is called an echo.
- 15. Reverberations It is the prolonged sound due to the merging of many echoes. The many echoes are produced because sound will be reflected off the different walls in a room.
- 16. Fishing boats use echoes to detect fish and measurement of the depth of the ocean War ships use echoes to detect mines Some animals use echoes to detect obstacles (like bats)
- 17. When describing a musical note as „high‟ or „low‟, we are actually talking about the pitch of the sound. Frequency affects pitch. High frequency – high pitch Lower frequency – lower pitch Shorter strings or air tunnels have higher frequency.
- 18. It is the volume of a sound. Loudness depends on the amplitude of the sound wave. Louder sounds have larger amplitudes and vice versa. It is measured in decibels (dB).