Waves
Wave Basics
- Waves transfer energy from one place to another without transferring matter.
- Wave speed is how quickly the wave is moving. It is measured in metres per second (m/s).
- Wavelength is the distance between each wave, measured from peak to peak or trough to trough.
- Frequency is the number of waves passing a point each second. It's measured in hertz (Hz).
- Amplitude is the maximum extent of a vibration or oscillation, measured from the position of equilibrium.
- The wave equation is v=fλ where v is wave speed, f is frequency, and λ is wavelength.
Types of Waves
- Transverse waves move the material perpendicular to the direction of the wave. Examples include light waves and waves on a string.
- Longitudinal waves move the material parallel to the direction of the wave. Examples include sound waves and ultrasound waves.
Wave Interactions
- When waves meet they can Interfere with each other, with the wave amplitudes adding together.
- Reflection happens when waves bounce back off a surface.
- Waves can be refracted, or change direction, as they enter a different medium.
- Diffraction is the spreading out of waves when they pass through an opening or around a barrier.
- Under certain conditions, waves can constructively interfere to produce a wave with larger amplitude, or destructively interfere to decrease or eliminate the wave amplitude.
Electromagnetic Waves
- Electromagnetic waves include radio waves, microwaves, infrared waves, visible light, ultraviolet radiation, X-rays, and gamma rays.
- They are all transverse waves and they all travel at the same speed - the speed of light (3 x 10^8 m/s) in a vacuum.
- As the frequency of the waves increases, so does their energy. This can make some electromagnetic waves particularly dangerous, such as X-rays and gamma rays.
Sound Waves
- Sound is produced by vibrations and travels as a longitudinal wave.
- The frequency of the vibrations determines the pitch of the sound, and the amplitude determines the loudness.
- Sound can be reflected, causing an echo, refracted as it enters different mediums, or diffracted as it spreads out from its source.
- Humans typically can hear frequencies between 20 and 20,000 Hz.
Waves in the Earth
- P-waves and S-waves are seismic waves created by earthquakes.
- Primary waves (P-waves) are longitudinal waves that can travel through solids and liquids.
- Secondary waves (S-waves) are transverse waves that can only travel through solids.
- Studying these waves can provide valuable information about the structure of the Earth's interior.