Waves Flashcards
(26 cards)
How do waves travel ?
Waves travel through a medium (substance). The particles oscillate (vibrate) and transfer energy. The particles stay in the same place.
Wavelength
the distance between adjacent waves (ie. from peak to peak or trough to trough)
Amplitude
the maximum displacement from a waves undisturbed position (the horizontal mid-line)
Frequency
the number of complete waves that pass a point every second. 1 wave per second has a frequency of 1Hz (hertz).
Time period
the time for a complete cycle of a wave
Time period equation….
𝑇= 1/𝑓
In transverse waves…
The oscillations (vibrations causing the wave) are perpendicular (90°) to the direction of energy transfer.
Examples of transverse waves
- all EM waves
- waves on water
- a wave on a string
In longitudinal waves…..
The oscillations are parallel to the direction of energy transfer.
Wave speed equation
𝑉=𝑓𝜆
Example of longitudinal wave..
Sound waves travel as a longitudinal wave in air.
Refraction
When waves change speed when they cross a boundary between two materials of different density.
If the wave enters a medium of higher density at an angle…..
the ray bends towards the normal
If it enters a medium along the normal then….
the wave does not change direction but the wavelength and speed decrease. )
Why does refraction happen ?
The part of the wave front that enters the more dense medium first, slows down as the rest of the wave front continues at the same speed but has to travel further. The difference in distance and speed causes the wave to refract
Wave experiment required
practical…
To measure the speed of sound:
1) two microphones held by a speaker (plugged into to a signal generator) can be connected to an oscilloscope.
2) One microphone is moved away from the speaker until the waves line up on the oscilloscope. The distance between the microphones is the wavelength. 3)Use V = fλ to find the speed of sound (f = whatever frequency the signal generator is set to). The speed of sound in air is 330 m/s.
4) The speed of water ripples and waves on a string can be investigated and calculated using the waves speed equation.
The electromagnetic spectrum
radio waves = 1-10(4)m = λ micro waves = 10(-2)m = λ infrared waves = 10(-5)m = λ visible light = 10(-7)m = λ ultra violet = 10(-8)m = λ x-rays = 10(-10)m = λ gamma rays = 10(-15)m = λ
wavelength decreases as you go up
frequency increases as you go up
Do all electromagnetic waves travel at the same speed through a vacuum ?
all electromagnetic waves travel at the same speed through a vacuum
Ultrasound
Ultrasound waves have a frequency higher than the upper limit for human hearing - above 20,000 Hertz (Hz).
Uses of ultrasound include:
- breaking kidney stones
- cleaning jewellery
P-waves
- longitudinal
- faster than S-waves
- can travel through solids and liquids
S-waves
- transverse
- slower than P-waves
- can travel through only solids
Seismic Waves
Shock waves travelling through the Earth, usually caused by an earthquake
What is a lens ?
A lens is a shaped piece of transparent glass or plastic that refracts light.
