Some stuff you should know… Waves Some stuff you should know…

The basics… Waves are everywhere… all the time. Everything in science is made of either matter or energy … matter is anything that occupies space and has mass (i.e. rocks, air, ice cream, iguanas, etc…) So what’s left ?...energy. Waves move energy but not matter through space.

The basics (continued) Energy can move in 1 of 2 ways… by collisions (think of a bat hitting a ball) or by vibrations. Vibrations are repeating types of motion that disturb their surroundings. A wave is simply the disturbance created by these vibrations (think of a rock dropped in a pond)

Two Types of Waves Electromagnetic Waves Mechanical Waves Do not require a medium (particles in a solid, liquid, or gas) to travel Light Radio waves Mechanical Waves Require a medium to travel Sound Waves Water Waves

2 types of wave movement 1.) Transverse wave – wave in which the displacement of the medium’s particles is at right-angles to the direction of the wave motion. Water ripples, stadium wave, electromagnetic waves, s-waves of earthquakes

2.) Longitudinal (Compressional) wave wave in which the displacement of the medium’s particles is in line with or parallel to the direction of the wave motion. Sound waves, p-waves in earthquakes

Longitudinal Compressional Wave Transverse Wave

Some vocabulary Crest – The uppermost part of a wave Trough – The lowest part of a wave Amplitude – The height of the crest or the depth of the trough Wavelength – The distance between 2 successive crests of waves. Frequency – The number of waves occurring over a period of time. Measured in hertz (Hz). 1 Hz = 1 cycle/ second

Sound Waves Can travel through solids, liquids and gases. Vibrates particles, which moves next particle, which moves next particle… Travel faster in solids and liquids than gas (i.e. air)… why? Because the speed of sound waves relies on how closely the particles are packed together… The closer the particles, the faster the sound

In sound waves… Frequency determines the pitch Pitch is how high or low the sound is Frequency is a measure of how many waves pass a point in a given time Hertz is the most common measurement of frequency and is cycles per second

Hearing Thresholds Humans 20- 20,000 Hz Bat 2,000-110,000 Hz Dogs 60- 45,000 Hz Why can’t humans hear dog whistles?

In sound waves… Amplitude measures volume or loudness. The common unit for sound waves is a decibel (dB)

Common Noises Whisper 30 dB Normal Conversation 60-70 dB Hearing loss after sustained exposure begins at 90-95 dB Pain begins at about 125dB Jet engine @ 100 ft, or gunshot 140 dB

Electromagnetic (EM) Waves A type of wave that doesn’t have to pass through a medium (i.e. doesn’t need solid, liquid or gas) The Sun is a big source… its waves pass through the vacuum of space. Radiation: the energy that the earth receives from the sun All forms of energy that travel through space as waves. The waves that make up all forms of radiation are known as electromagnetic waves.

RMIVUXG Examples include: Radio waves, microwaves, infrared rays visible light, ultraviolet, X-rays, and gamma rays. This is the Electromagnetic Spectrum and it is arranged by wave length.

http://lot.astro.utoronto.ca/images/spectrum.png

Wave lengths Wave lengths determine energy Radio waves have long wave lengths LOW energy Gamma waves have very short wave lengths HIGH energy

Using waves of the EMS Radiation therapy for cancer patients is high energy. Past visible light waves can cause damage to humans via skin burns and cell damage Microwaves don’t actually use microwaves! Most microwaves use radio waves Remember radio waves are not SOUND WAVES

Combining Radio and Sound Radio waves (EMS) travel through the air without being heard or seen Sent by transmitter Antennas pick up radio waves or help receiver pick up radio waves Receivers transfer radio waves to sound waves in your stereo You control how the stereo produces the vibrations that cause sound or the frequency of radio waves your stereo receives.

Changing waves Diffraction – when a wave bends around a barrier Water around a boat, light around a table Reflection- Waves bouncing back Echo in sound waves Mirror image in light waves Refraction- Waves bending as they pass through a different medium Prisms separate light by refraction ROY G. BIV

Wave Goodbye !