Waves Flashcards
(22 cards)
What is a Progressive Wave?
A wave that transfers energy from a source through the surroundings by means of oscillations
What is a Longitudinal Wave?
A wave where vibrations are parallel to the direction of energy transfer
What is a Transverse Wave?
A wave where vibrations are perpendicular to the direction of energy transfer
What is Displacement?
The Distance of a point on a wave above or below the undisturbed position
What is Amplitude?
The Maximum Displacement of the wave from it’s undisturbed position
What is Wavelength?
The Distance between two adjacent points in phase
What is Time Period?
The time taken for one complete oscillation
What is Frequency?
The number of wavelengths per unit time
CRO
Cathode Ray Oscilloscope
Connected to a microphone
Sound waves amplitude on the Y-axis as voltage
X-axis represents time
Need to know voltage scales and time base
The Wave Equation
v = f x λ
v: speed in metres per second
f: frequency in Hertz
λ: Wavelength m
Conditions for wave speed
Speed depends on the medium the wave is travelling through
For electromagnetic waves in a vacuum (consider air to be a vacuum) the speed is c: 3 x 10^8
What are the wave phenomena for Transverse Waves?
Reflection; Refraction; Diffraction; Interference; Polarisation
What are the wave phenomena for Longitudinal Waves?
Reflection; Refraction; Diffraction; Interference
Ripple Tank
A plane (straight) bar of wood driven by an electric motor vibrates on top of the water
Frequency of oscillations is determined by the frequency of the motor
Wavelength and Frequency of the waves are determined by the motor
Wave speed depends on the medium or depth the wave is travelling through
Lower depth reduces wave speed
What is Phase Difference?
The angle by which a wave lags or leads another as an angle
Also applies to two points on the same wave
What is In Phase?
A phase difference of 0 or 360
What is Antiphase?
A phase difference of 180
What is Intensity?
The radiant power passing through a surface per unit area
Intensity Equation
I = P/A
I: Intensity of a wave at a surface (Watts per Metre squared)
P: Radiant power passing through the surface (Watts)
A: Surface area (Metres squared)
Intensity and Distance
As a wave travels from a source the radiant power spreads out reducing the intensity
From a point source the energy and power spread uniformly in all directions giving the surface area of a sphere ( 4πr^2)
Power at a distance r from the source, the area is equal to the area of a sphere
I and r^2 are inversely proportional
Intensity and Amplitude
Intensity ∝ Amplitude ^ 2
Amplitude ∝ √Intensity
Equation Linking Time Period and Frequency
T = 1/F
