Students will learn about waves

• Waves transfer energy without the transfer of mass.
• A wave is a vibratory disturbance that is transmitted through a material or through space.

• Mechanical waves require a material medium for transmission. The energy disturbance is propagated by the molecules of water, air, or a spring.
– Transverse waves exhibit simple harmonic motion about a rest position perpendicular to the direction of motion. (EX: waves on a string)
– Longitudinal waves exhibit SHM parallel to the direction of motion (EX: sound, slinky)
– Surface wave exhibit motion both parallel and perpendicular to the direction (EX water waves)

• Electromagnetic waves do NOT need a material medium for transmission. They can travel in a vacuum. (EX: light)

• The time it takes for a wave to repeat itself
• Measured in seconds

• Number of waves per second
• Frequency is the inverse of period
• Measured in Hertz (older measurements in
1/second or second^(-1))

• Amplitude is the maximum displacement of any particle in the medium relative to its rest position.
– In a transverse wave the maximum upward displacement is the “crest” and the minimum downward displacement is the “trough”
– In longitudinal waves the particles produce region of maximum compression called condensations and minimum compression called rarefactions.
– Amplitude is related to the energy carried by the wave.
– Amplitude in sound is Loudness; in light it is brightness.

• The distance between two successive points on a periodic wave is the wavelength.
• Wavelength is measured in meters.
• Wavelength is symbolized by the Greek letter lambda.

• Speed = wavelength x frequency (m/s)
• Wavelength = speed/frequency

• What is the wavelength of a sound wave whose speed is 330 m/s and whose frequency if 990 Hertz?
•
• Speed = wavelength x frequency
• Wavelength = speed/frequency
= 330 m/s/990 = 0.33 m

• All electromagnetic waves travel in space at the speed of light, c, equal to 3 x 10^8 m/s
• (Einstein showed that nothing can exceed the speed of light, c = 3 x 10^8 m/s)