WAVES Mr. Banks 8 th Grade Science
WAVES A wave is a disturbance that transfers, or carries energy from one place to another. Classified by what they move through For mechanical Waves energy is transferred by vibrations of a medium (medium = matter, stuff) ex/ ocean waves move through water For electromagnetic waves (EM Waves) energy moves through disturbances in the electromagnetic field.
WAVE STRUCTURE CREST (peak) AMPLITUDE WAVELENGTH TROUGH
WAVE STRUCTURE Wavelength the distance between the same point in two waves. Amplitude the distance from the middle of the wave to the maximum crest or trough. Frequency The number of waves that pass a specific point each second.
MECHANICAL WAVES Mechanical waves are waves that require a medium to transmit their energy. Travel through & gradually lose energy to that medium. Examples: water, sound, rope, & spring waves Mechanical wave media: water, air, rope, spring
MECHANICAL WAVES transverse Longitudinal surface
TRANSVERSE WAVES Particle vibration is perpendicular (sideways or up and down) to the direction of the motion of the wave Examples: Guitar strings Electromagnetic waves (ex: light)
LONGITUDINAL WAVES Particle vibration is parallel to the direction of the motion of the wave (back and forth). Also called compression or pressure wave. Instead if crests and troughs, there are alternating areas of compression and rarefaction. Examples: Sound waves P-type earthquake waves Rarefraction (expansion) Compression
SURFACE WAVES Particle vibration is in a circular motion. Occur at the boundary between two different mediums. Particles move more the closer they are to the surface. Example: Ocean waves
AMPLITUDE Distance between the middle & crest or middle & trough The amplitude is directly related to the power of a wave Does not affect the velocity of a wave Determines strength (earthquake), loudness (sound), or brightness (electromagnetic wave)
WAVELENGTH Distance between any two repeating points on a wave crest-crest, trough-trough, rarefraction-rarefraction, compression-compression
WAVELENGTH For waves moving at the same speed, Shorter wavelengths have a higher frequency because the waves aren t as long
WAVELENGTH Determines What colors we see. What sounds we hear (pitch). Shorter wavelengths are higher pitched.
Frequency ƒ The number of waves that pass a specific point each second. measured in Hertz (Hz) = number of wavelengths passing a spot in 1 second.
VELOCITY v the rate (speed) at which the wave travels. Wave speed depends on medium. Mechanical waves travel faster through dense mediums. EM Waves are faster through less dense mediums (space)
Calculating wave velocity 1. What is the wavelength of a water wave if its frequency is 4 Hz and its velocity is 12 m/s? 2. Calculate the velocity of a wave if the frequency is 54 Hz and the wavelength is 25 m. 3. Calculate the velocity of a wave if the frequency is 120 Hz and the wavelength is 65 m. 4. What is the wavelength of a water wave if its frequency is 33 Hz and its velocity is 7 m/s? 5. What is the wavelength of a water wave if its frequency is 7.5 Hz and the wave speed is 53 m/s?
Which is a longitudinal wave, and which is a transverse wave?
Wave reflection Reflection occurs when waves change directions as a result of "bouncing off" a surface like a mirror.
Wave refraction The bending of a wave when it enters a medium where its speed is changed.
Different temperatures of air allow waves to travel at different speeds. This means that they cause refraction. Extreme differences in temperature (like in the desert) can cause light waves to bend and make mirages.
Wave diffraction A change in the direction of a wave as it passes through an opening or around an object in its path.
Wave interference Two waves can interact with one another, this interaction is called interference. Constructive Destructive
Wave interference Copyright 2010 Ryan P. Murphy
Waves can be absorbed by objects and converted into other types of energy. For example, light waves can be absorbed by objects and are usually converted into heat. However, if they strike a solar panel that light can be converted into electricity.