Wavelength, Frequency & Period
Þ All waves are described by a set of basic parameters.
Þ Wavelength:
· Defined as the separation between two wave crests.
· Measured using many different linear units: kilometers (km), centimeters (cm), microns (m), nanometers (nm), etc.
· Usually expressed using the Greek letter l
Þ Frequency:
· Defined as the number of waves which pass an observer’s location in a specific time interval.
· Measured in cycles per unit time, most commonly cycles per second.
· Usually expressed using the Greek letter n
· 1 cycle per second = 1 Hertz, abbreviated Hz
· 103 Hz = 1 KHz = one kilohertz (AM radio frequencies)
· 106 Hz = 1 MHz = one megahertz (FM radio frequencies)
Þ Period:
· Defined as the time it takes to complete one wave cycle. Period is the inverse of the frequency.
· Usually expressed using the English letter p
· Period = 1 divided by the frequency (1 ¸ p)
· Frequency = 1 divided by the period (1 ¸ n)
Þ Amplitude:
· Defined as the strength or height of a wave.
· Measured in linear units (meters) for a sound or ocean wave. For EM waves, amplitude is often expressed in units of energy per time.
Þ Speed:
· The speed of a wave = the wavelength times the frequency
· v = l n
· All electromagnetic waves travel at the same speed, 300,000 km per sec.