Waves Flashcards
wavefront
A line of points in phase with each other in a wave, perpendicular to the direction of energy transfer
Radio
-1 to 6m
Infrared
-3 to 7x-7
Visible
7x-7 to 4x-7m
Ultraviolet
4x-7 to -8m
X-rays
-8 to -10m
Gamma
-10 to -16m
Wave Speed
the distance travelled by a wave per unit time
Frequency
the number of complete wavelengths passing a given point per unit time
Period
the time taken for a full oscillation of one wavelength to pass a given point
Wavelength
the minimum distance between two adjacent points on a wave oscillating in phase
Amplitude
the maximum displacement from the origin
displacement
the distance from the equilibrium position in a particular direction
phase difference
difference in displacement between two particles on a wave/different waves
micro
-1 to -3m
Principle of Superposition
when two waves meet at a point, the resultant displacement of the wave at that point is equal to the sum of their individual displacements.
Node
A point on a standing wave that always has no displacement from the rest position
Antinode
A point of maximum displacement midway between two nodes in a standing wave
Polarised light
Transverse wave in plane normal to the direction of energy propagation. Oscillations in one direction are confined to a single plane.
wave
the transfer or storing of energy through a medium by oscillations of the particles in that medium
Total Internal Reflection
the complete reflection that takes place within a substance when the angle of incidence of light striking the surface boundary is more than the critical angle
Speed of light in water
2.25 x 10^8 m/s
Refractive Index Glass
1.5
Refractive Index Water
1.3
Polaroids
transparent polymers. long chain molecules that absorb molecules
Polarisation
Oscillations of a transverse wave are limited to only one plane
Refraction
A wave changes direction as it changes speed, when it enters a new medium. partial reflection occurs.
Reflection
A wave changes direction at a boundary between two media, remaining in the original medium.
Diffraction
The spreading out of a wave front as it passes through a gap or around an obstacle.
Intensity
The radiant power passing at right angles through a surface per unit area
Similarity between progressive/standing waves
Both have frequency/wavelength/period
2 differences between standing and progressive
Adjacent particles have same max. amplitude on progressive, different amplitudes on standing. Progressive waves transport energy from source to absorber, standing waves store energy.
Electron circles
Diameter of circle is proportional to wavelength of electron
Intensity definition
the rate of flow of energy per unit area at right angles to direction of travel of wave.
What are the 6 different wave phenomena?
Reflection, refraction, polarisation, diffraction, superposition, interference
How would you change wave speed in a wave tank?
Change depth of water.
How do sunglasses reduce glare?
reflected light from surface is partially plane polarised
polarising sheet is placed at right angles to reflected light plane
What does ‘in phase’ mean?
Two points are in phase if they are at the same point in a wave cycle.
Coherence definition
Two waves are coherent if they have the same wavelength, frequency and fixed phase difference
What is the path difference?
The length of one wave’s path minus the length of the other wave’s path.
What is the path difference for constructive interference?
nλ
What is the path difference for constructive interference?
nλ
Interference definition
When two or more waves superpose and there is an overall change in displacement.
Why do we use more slits?
Maxima get brighter and narrower, minima get dimmer, more precise measurements
What happens if you use white light instead of a monochromatic light source in a diffraction experiment?
Central white fringe, maxima become spectra, because different wavelengths in white light are diffracted different amounts.
What is a stationary wave?
The superposition of two progressive waves with the same wavelength, moving in opposite directions.
How to test whether waves are plane polarised?
Take polaroid/metal grille and rotate it in front of transmitter with detector behind. If reading of 0 occurs, then they are plane polarised.
