4. Waves Flashcards
Simple harmonic motion
When the direction of the force is always towards the fixed point and the magnitude is proportional to the displacement from the fixed point.
Time period (SHM)
The time taken for a complete cycle.
Frequency (SHM)
The number of complete cycles per second.
Amplitude (SHM)
The maximum displacement of the particle.
Displacement (SHM)
The displacement of the particle from the equilibrium position (in single direction).
Phase difference
The x shift between two sin waves.
Isochronous oscillations
Oscillations with the same time period no matter what amplitude change changes due to damping occur.
Travelling wave
A wave that transfers energy form one place to another.
Wavelength (waves)
The shortest distance between two points that are in phase.
In phase
Two particles are in phase if they are moving in the same direction at the same time (an integer no of wavelengths apart)
Frequency (waves)
The number of peaks/troughs passing a point per second OR the number of vibrations per second performed by the source.
Period (waves)
The time taken for a complete wavelength to pass a point OR a particle to undergo one complete oscillation.
Wave speed
The speed at which a point on a wave is moving through a medium.
Transverse
A wave where the direction of oscillation is perpendicular to the direction of energy transfer.
Longitudinal
A wave where the direction of oscillation is parallel to the direction of energy transfer.
Wavefront
A surface that travels with a wave and is perpendicular to the direction of movement.
Ray
A line showing the direction of energy transfer and is perpendicular to the wavefront.
Amplitude (waves)
The maximum displacement of a vibration or oscillation, measured from the position of equilibrium.
Intensity
The power transferred per unit area.
Superposition
When two waves meet at a point the resultant amplitude is the vector some of the amplitudes of the two waves.
Polarization
the action of restricting the vibrations of a transverse wave, especially light, wholly or partially to one direction.
Plane polarized
When the direction of vibration stays constant over time
Partial polarization
When there is some restriction to the direction of vibration but not 100%.
Malus’s Law
When plane polarised light is incident on an analyser, the intensity of the light transmitted by the analyser is directly proportional to the square of the cosine of the angle between the transmission axes of the analyser and the polariser. I is prop to 1/cos^2(theta)
Optically active
The ability to rotate the plane of plane polarized light.
Polarimeter
Measures angle light is rotated.
Huygen’s principle
Every point on a wavefront is a source of wavelets. These wavelets spread out in the forward direction, at the same speed as the source wave. The new wavefront is a line tangent to all of the wavelets.
Absolute refractive index
the ratio of the speed of light in a vacuum to that in the given medium
Snell’s law
for waves of a particular frequency and for a chosen pair of media the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant called the refractive index.
total internal reflection
the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.
Coherent light =
light with the same frequency/wavelength that are in phase.
Diffraction =
the bending of a wave as it passes around an object or through a slit.
Path difference =
the difference in distance travelled by two waves that meet at a point.
node
a point on a standing wave where interference is destructive
antinode
a point on a standing wave where interference is constructive.
standing wave
a wave where the positions of the peaks and troughs do not change.
