1. Waves A wave is a disturbance that transfers energy from one place to another Waves transfer energy without moving the matter Waves require energy and forces: water, earthquakes A medium is a substance that a wave moves through like matter Waves that transfer energy through matter are known as mechanical waves – earthquakes, water, sound, rope Waves can also be classified by how they move

2. Types of Waves Longitudinal – The displacement of particles is parallel to the direction of the wave. – Sound waves that travel through the air are longitudinal – Imagine the coils in a slinky as they spring from one end to the other

3. Types of Waves Transverse – The displacement of particles is perpendicular to the direction of the wave. Transverse means “across” – Ripples on a pond are Transverse waves. – Imagine the motion of a sting on an instrument as it is plucked.

4. Waves have properties that can be measured like speed, amplitude, wavelength, and frequency A crest is the highest point, or peak A trough is the lowest point or valley Amplitude for a transverse wave is the distance between a line through the middle of a wave and a crest or trough. Amplitude indicates how much energy the wave is carrying The distance from crest to crest (or trough to trough) is the wavelength The number of waves passing a fixed point in a certain amount of time is called its frequency (the unit for frequency is the Hertz (1/s)) Frequency and wavelength are related in that as frequency goes up wavelength goes down, etc.

5. Wave Calculations You can calculate the speed of a wave Speed = wavelength (λ) x frequency Make a wavelength triangle Waves travel at different speeds – light travels a million times faster than sound (761 mph)

6. Wave Interactions The motion of a wave changes when it encounters a new medium Refraction, reflection, and diffraction The bouncing back of a wave after it strikes a barrier is called reflection (mirror/echo) Newtons third law Waves that encounter an new medium at an angle causing it to bend is called refraction Occurs b/c waves travel at different speeds through different mediums Waves that encounter a barrier w/ an opening pass through and spread out, this is called diffraction

7. Interference Waves can also interact with other waves, adding or subtracting energy in the place where they meet This is called interference When 2 waves crests and troughs are aligned you add their amplitudes together, called constructive interference When 2 waves crest and troughs align, you subtract their amplitudes called destructive interference When identical waves meet, they are usually not aligned

8. Soun d Sound is a mechanical wave produced by a vibrating object Sound is a longitudinal wave Sound travels faster in liquids and fastest in solids…the greater the temperature, the faster the sound wave will travel

9. Frequency & Pitch Pitch is the characteristic of highness or lowness of a sound The frequency of a sound wave determines pitch High frequency = high pitch; low frequency = low pitch Sounds that vibrate faster have high pitch The unit for pitch is the Hertz (Hz) Humans can hear sounds from 20 to 20,000 Hz Dogs, bats, and dolphins can hear in the ultrasound range (super high frequency) The Doppler effect is the change in pitch that occurs when a source of sound is moving – ambulance/train

10. Amplitude of Sound The intensity of a sound wave is how much energy it has A decibel (dB) is used to measure this The greater the amplitude, the more intense a sound wave has and the louder it will be Amplification is used to make sound waves bigger

11. Electromagnetic (EM) Waves You see and feel these waves when you see light or feel heat; used by radio, TV, cell phones An electromagnetic wave is a disturbance that transfers energy through a field A field is an area around an object where the object can apply a force on another object w/o touching it (ex. Magnets on metal) Most of the EM waves come form the Sun, many from human technology Energy that moves in the form of EM waves is called radiation Different from a mechanical wave b/c a mechanical must vibrate the medium as it moves, which uses some of its energy EM waves do not require a medium and in theory can travel forever EM waves travel at the speed of light (186,000 mi/s)

12. How EM Waves Form EM waves occur when electrically charged particles move A moving charged particle has a magnetic field around it When electrically charged particles move quickly, they can start a disturbance (wave) of electric and magnetic fields, which vibrate at right angles to each other When EM waves move through a vacuum, its all potential energy When they encounter matter, energy is transferred to different forms

13. Light Interacts w/ Materials Most common reflection; why you see Transmission is passage of EM wave through a medium, air, windows, etc. Absorption is the disappearance of an EM wave into a medium; limits light that is transmitted or reflected Materials can be transparent, translucent, and opaque Light is scattered in all directions – why sky is blue When light interacts with a prism it spreads light out to different wavelengths You see color b/c that object reflects that wavelength of light back to your eyes