Chapter 11, 12 - Waves Flashcards
What are Progressive Waves?
Progressive waves are waves which transfer energy in the same direction as the wave.
Define Displacement of a Wave.
How far the oscillating particle moves from it neutral position, measured in metres.
Define Amplitude.
Amplitude is the maximum magnitude of displacement of the oscillating particles, measured in metres.
Define Wavelength.
Wavelength is the length of one whole wave cycle (peak to peak), measured in metres.
Define Period of a Wave.
The Period of a Wave is the time taken for 1 whole wavelength, measure in seconds.
Define Frequency.
Frequency is the number of complete cycles passing a point per second, measured in Hertz.
Define Phase.
Phase is a measure of the position of a certain point along the wave cycle, measured in degrees or radian.
Define Phase Difference.
Phase Difference is the amount 1 wave lags behind another, measured in degrees or radians.
How are Frequency and Period related?
Frequency equals the reciprocal of the period.
f = T⁻¹
What is the equation for Wave Speed?
Wave speed (ms⁻¹) = Frequency (Hz) x Wavelength (m)
What are the Key Features of a Transverse Wave?
- Progressive Wave.
- Oscillations are perpendicular to the direction of Motion.
- Made up of Peaks and Troughs.
- Shape is like a Sine Graph.
- Can Travel in a Vacuum.
What are the Key Feature of Longitudinal Wave?
- Progressive Wave.
- Oscillations are parallel to the direction of motion.
- Made up of Compressions and Rarefactions.
- Cannot travel in a Vacuum.
Define Intensity.
Intensity is defined as the rate of flow of energy per unit of area at right angles to the direction of travel of the wave.
Intensity (Wm⁻²) = Power (W) / Area (m²)
How is Intensity proportional to Amplitude?
Intensity ∝ (amplitude)²
What Properties do EM Waves have in Common?
- Travel at 3 x 10⁸ ms⁻¹.
- Transverse waves, so progressive.
- Oscillating electric and magnetic field perpendicular to each other and the direction of the wave.
- Can be reflected, refracted, diffracted.
- Can be Polarised.
What is the Electromagnetic Spectrum?
Royal Marines Invade Vietnam Using X-ray Guns Radio Micro Infrared Visible Ultra Violet X-ray Gamma
What are the Wavelength Boundaries for the EM Spectrum?
Radio: 10⁻¹ - 10⁶ Micro: 10⁻³ - 10⁻¹ Infrared: 7x10⁻⁷ - 10⁻³ Visible: 4x10⁻⁷ - 7x10⁻⁷ Ultraviolet: 10⁻⁸ - 4x10⁻⁷ X-ray: 10⁻¹³ - 10⁻⁸ Gamma: 10⁻¹⁶ - 10⁻¹⁰
What is Polarisation?
Polarisation is when you pass a transverse wave through a filter, restricting it to only 1 plane.
What happens when you pass a transverse wave through a filter then another filter but rotated 90°?
When the wave places through the first filter it will be restricted to 1 plane, however when it passes through the next filter it will be restricted to a different plane, with no energy. Ergo, there will be no remaining wave.
How does a polarising grid polarise Microwaves?
- The wavelength of microwave is too long to be polarised by a filter, so a metal grid is used.
- Electric field excites the electrons in the metal grill.
- Energy of wave is absorbed and re-emitted on 1 plane in all directions.
- Only a few of the re-emitted waves are in the same direction as the original wave.
What is Diffraction?
Diffraction is when a wave passes through a small gap causing the wave to ‘spread’ out.
Diffraction is at its greatest when the gap is width as the wavelength.
How can diffraction be investigated?
- Using a ripple tank and an oscillating paddle.
- Using different sized gaps, you can visually see diffraction and what effects it.
What is reflection?
Reflection is when a wave bounces off a surface boundary causing it to change direction.
The angle of incidence is equal the the angle of reflection.
What is Refraction?
Refraction is when a wave change direction as it is slowed or sped up as it enters a different medium.
Ray bends towards normal, the ray has entered a slower medium. And Vice Versa.
Angles crossing the boundary are equal, incident.
Angles after crossing the boundary are equal, refraction.
