Waves Flashcards
What are Mechanical Waves?
Waves where energy is transferred through a medium
What are Progressive Waves?
Waves which transfer energy as a result of oscillations of the medium through which the energy is travelling
What are Longitudinal Waves?
Waves whose oscillations are parallel to the direction of energy transfer
What are Transverse Waves?
Waves whose oscillations are perpendicular to the direction of energy transfer
What is Wavelength?
Distance a wave travels as it completes one full wave cycle
Can be measured by the difference in distance for corresponding points on consecutive wave cycles
What is Frequency?
Number of Wavelengths passing through a point in a period of time
(Inversely proportional to the Time Period)
What is the Time Period?
Time taken for one complete wavelength to pass a certain point
(Inversely proportional to Frequency)
What is Wave Speed?
What is the Wave Equation?
The distance a wave travels in a period of time
v = fλ
What is Displacement?
The distance moved from the equilibrium for a point on a wave
What is Amplitude?
Maximum displacement from the equilibrium
What is Phase Difference?
The angle seperating two points on a wave cycle
What are the conditions of Phase Difference for waves to be ‘In-Phase’, ‘in Anti-phase’ & ‘out of Phase’?
In-Phase = 2n(180’)
Anti-phase = n(180’)
(where n is a whole number)
Out of Phase = anything else
What is Path Difference?
Distance seperating two points along a wave cycle
What are the conditions of Path Difference for waves to be ‘In-Phase’, ‘in Anti-phase’ & ‘out of Phase’?
In-phase = nλ
Anti-phase = (n + 0.5)λ
(where n is a whole number)
Out of Phase = anything else
How do you convert Radians to Degrees?
Rad. x (180/π)
How do you convert Degrees to Radians?
Deg. x (π/180)
How many radians in a full wave cycle?
2π radians
How many degrees in a full wave cycle?
360 degrees
What are the 4 ways a wave can be impacted by its surroundings?
Reflection - Wave changes direction at a boundary between two media (remaining within original medium)
Refraction - Changes direction of Light as it transitions from one medium to another - due to change in speed of travel
Diffraction - When a wave moves through a slit, the wave spreads out after passing through the gap
Polarisation - When light is restricted to oscillating in a single plane
What is Intensity?
The radiant power transferred per unit Area
What is the relation between Wave Intensity and Amplitude?
Intensity is directly proportional to Amplitude squared
What is an Electromagnetic Wave?
Transverse Waves created when an Electric Field and Magnetic Field couple together
They do not need a medium to oscillate in
What is the order of the EM Spectrum?
Radio, Micro, Infrared, Visible, UV, X-ray, Gamma
What is the range of wavelengths and frequencies for Radio Waves?
> 10^-1 m
<3x10^9 Hz
What is the range of wavelengths and frequencies for Microwaves?
10^-1 - 10^-3 m
3x10^9 - 3x10^11 Hz
What is the range of wavelengths and frequencies for Infrared Radiation?
10^-3 - 7x10^-7 m
3x10^11 - 4x10^14 Hz
What is the range of wavelengths and frequencies for Visible Light?
7.8 - 3.9 x 10^-7 m
4.0 - 7.5 x 10^14 Hz
What is the range of wavelengths and frequencies for UV Light?
3.9x10^-7 - 10^-8 m
10^16 - 10^18 Hz
What is the range of wavelengths and frequencies for X-Rays?
10^-8 - 10^-12 m
10^18 - 10^20 Hz
What is the range of wavelengths and frequencies for Gamma Rays?
<10^-12 m
>10^20 Hz
What is Polarisation?
When a transverse wave is filtered so that is oscillates in a single plane
What happens when a light travels through two parallel polarising filters?
The light will simply be Plane Polarised - passing through the second filter without any changes
What happens when a light travels through two perpendicular polarising filters?
No light will be able to pass through the second filter
(First filter polarises light to a single plane, which is then blocked by the second filter)
What is the Refractive Index of a medium?
The ratio between Speed of Light in a Vacuum and the Speed of Light in the medium
n = c / v
What is Snell’s Law?
n1.sinΘ1 = n2.sinΘ2
What happens to the Speed of Light as it enters a medium with a higher refractive index?
Light slows down and angles towards the normal
What happens to the Speed of Light as it enters a medium with a lower refractive index?
Light speeds up and angles away from the normal
What is the Critical angle of a medium?
The angle of incidence at the boundary between two media that will produce an angle of refraction of 90’ from the normal.
(Run along the boundary of the medium)
What is the equation for the Critical Angle?
Sin C = n2 / n1
What is Total Internal Reflection?
The reflection of all light back into the original medium when hitting a boundary between two media
What are the stipulations for Total Internal Reflection?
The original medium will have a higher refractive index and the angle of incidence must be greater than the Critical Angle
