Waves Flashcards
define a progressive wave
A moving wave that carries energy from one place to another without transferring any material in which the direction of energy transfer is the same as the waves direction of travel
def phase difference
The amount that one wave lags behind another
What is the equation for frequency in terms of the period?
Frequency = 1 / Period
How does an oscilloscope work?
A cathode ray oscilloscope measures voltage. It displays waves from a signal generator as a function of voltage over time.
What is the name of the wave on an oscilloscope?
A trace
What are the squares on an oscilloscope called?
Divisions
What is the timebase on an oscilloscope?
The horizontal axis is the timebase (the amount of time per division)
How would you calculate wave frequency from an oscilloscope?
Find the period by counting how many divisions in one full oscillation of the wave and then multiply by the timebase. Then do 1 / Period to get frequency.
What two dials are on an oscilloscope and can help make them easier to read?
The gain dial (changes volts/div) and the timebase dial (changes time(ms)/div)
What direction do transverse waves vibrate with respect to the direction of movement?
At right angles to the direction of movement
What direction do longitudinal waves vibrate with respect to the direction of movement?
Parallel to the direction of movement
What is the name for the points on a longitudinal wave where the waves are close together and far apart?
Compression (close) and rarefaction (far)
How can you identify the wavelength of a longitudinal wave?
From one compression/rarefaction to another
Define the intensity of a wave
Intensity is the rate of flow of energy per unit area at right angles to the direction of travel of the wave
What is the equation and unit for wave intensity?
Intensity (W/m^2) = Power (W) / Area (m^2)
Intensity is proportional to…
Amplitude squared
What types of fields are the waves on the EM spec
Electrical and magnetic
Can EM waves be polarised?
Yes, since they are all transverse
What is the full EM spec?
Radio, Micro, Infrared, Visible light, Ultraviolet, X-Ray, Gamma
What is the approximate wavelength of radio waves? (m)
10^-1 - 10^6
What is the approximate wavelength of microwaves? (m)
10^-3 - 10^-1
What is the approximate wavelength of infrared light? (m)
7x10^-7 - 10^-3
What is the approximate wavelength of visible light? (m)
4x10^-7 - 7x10^-7
What is the approximate wavelength of ultraviolet light? (m)
10^-8 - 4x10^-7
What is the approximate wavelength of X-rays? (m)
10^-13 - 10^-8
What is the approximate wavelength of gamma rays? (m)
10^-16 - 10^-10
What are some uses of radio waves? (1)
Radio transmmissions
What are some uses of microwaves? (3)
Radar, cooking, TV transmissions
What are some uses of infrared light? (4)
Heat detectors, night vision cameras, remote controls, optical fibers
What are some uses of visible light? (2)
Human sight, optical fibers
What are some uses of ultraviolet light? (2)
Sunbeds, security marks
What are some uses of X-rays? (3)
Medical imaging, Airport security scanners, radiotherapy (cancer treatment)