I. Properties of waves and sound.
a. Know and be able to describe the following:
Wave: A disturbance that transfers energy from place to place
Transverse wave: A wave that moves the medium in a direction perpendicular to the direction in which the wave travels. λ (wavelength): The distance between two corresponding parts of a wave.
Compressional/longitudinal wave: A wave that moves a medium in a direction parallel to the direction in which the wave travels.
Intensity: The amount of energy per second carried through a unit area by a wave
Loudness: Perception of the energy of a sound
Amplitude: The max distance the particles of a medium move from their rest positions as a wave passes through the medium. (Distance from crest or trough to rest position)
Medium: The material through which a wave travels.
Crest: The highest part of a transverse wave.
Trough: The lowest part of a transverse wave.
Rarefaction: The part of a longitudinal wave where the particles of the medium are far apart.
Compression: The part of a longitudinal wave where particles of the medium are close together.
Infrasonic: Sound waves with frequencies below 20 Hz (human audibility).
Ultrasonic: Sound waves with frequencies above 20,000 Hz (human audibility).
Frequency: The # of complete waves that pass a given point in a certain amount of time
Pitch: Perception of the frequency of a sound.
Doppler Effect: The change in frequency of a wave as its source moves in relation to an observer. Pitch of a moving sound is higher when closer; crests are closer together.
Velocity: The speed of something in a given direction.
Speed of sound: At 20 degrees Celsius, about 343 m/s. Direct variation between elasticity and sound/ temp. and sound. Inverse variation between density and sound.
Wave interference: The interaction between waves that meet.
Constructive: When waves combine to make a wave with a larger amplitude
Destructive: When waves combine to make a wave with a smaller amplitude
Resonance: The increase in the amplitude of a vibration that occurs when external vibrations match an object’s natural frequency.
Closed-end air column: Consists of a tube with one end closed off. Refer to packet.
b. Transverse Wave: Draw a transverse wave diagram when given amplitude, wavelength.
II. The Electromagnetic Spectrum http://www.darvill.clara.net/emag/index.htm
a. List the 7 types of electromagnetic radiation in order from longest to shortest wavelength. Relationship between frequency and wavelength of an EM wave?
Radio wave, Microwave, Infrared, Visible light, Ultraviolet, Soft X-Rays, Hard X-Rays, Gamma Rays
The higher the frequency, the lower the wavelength
Wavelengths above visible light: waves. Shorter: Rays
b. The colors of visible/optical light: Know the 7 colors in order from lowest energy.
Lowest energy: RED. Then ORANGE, YELLOW, GREEN, BLUE, INDIGO, VIOLET!
Note: Red has the longest wavelength
c. How is photon energy related to wavelength/frequency of electromagnetic waves?
Wavelength: Inverse variation between photon energy and wavelength
Frequency: Direct variation (as energy increases, so does frequency)
d. Applications and dangers of electromagnetic radiation: What are the major uses and dangers of the seven types of electromagnetic radiation?
Communications (like radio stations)
Large doses can cause cancer
Speed cameras, microwave ovens, cell phone
Prolonged exposure can cause cataracts and affect parts of the brain
Study plant growth, heat, determine weather patterns, thermogram, heal injuries, remote controls, electric stoves
Rainbow!! Also used for light sources, and to see things
Too much light can damage the retina
Kill bacteria, stimulate vitamin D production in skin cells, treats jaundice in newborns
Sunlight can burn skin- skin cancer and eye