waves Flashcards
What is a transverse wave ?
Particle oscillation is perpendicular to the direction of energy transfer
What is a longitudinal wave ?
Particle oscillation is in the same direction as energy transfer
What is a standing/stationary wave ?
- 2 waves from fixed points creating a singular wave
What is a node ?
Points on a stationary wave that have no displacement
What is an antinode ?
Points on a stationary wave that have maximum displacement
What are the criteria for a stationary wave to form ?
- the same frequency
- similar amplitudes
- travelling in opposite directions
What happens if polarised light passes through a second polaroid filter at a different angle ?
No light passes through
What is an example of polarised light ?
3D film glasses -> enhances the viewing experience
How do 3D film glasses work ?
Each glass lens is 90° to the other, each eye sees a different image
What is constructive interference?
When a peak meets a peak, it creates a peak twice as big
What is destructive interference?
When a peak meets a trough, they create a flat surface
What is the first harmonic ?
When a standing wave creates half a wavelength
What does the μ stand for in the equation for the first harmonic ?
Mass in 1 metre
What is refraction ?
Bending of a wave when it changes mediums
What is the normal ?
Line at 90° to the boundary between 2 mediums
What is the angle of incident ?
Angle between the light coming in and the normal
What is the angle of refraction ?
Angle between the refracted light and the normal
How to find the percentage uncertainty?
( uncertainty / value ) x 100
What is the refractive index of air ?
1.0
What happens to wavelength as you go further down the rainbow ?
it gets shorter
🟥 🟧 🟨 🟩 🟦 🟪
longest ———————shortest
What is the critical angle ?
Where the angle of refraction is 90°
What happens when the critical angle is more than angle of incidence ?
Refraction
small reflection
What happens when the critical angle is equal to the angle of incidence ?
Refraction at 90°
small reflection
What happens when the critical angle is less than angle of incidence ?
Total internal reflection, all light reflected
What is the use of the cladding in an optic fibre ?
- stop dispersion
- protect the core (and light leakage)
What is light dispersion ?
Light of different colours/speed arrive at different times
Overcome by using monochromatic light
What is multimode dispersion ?
Light at different angles arrives at different times
Reduced by increasing refractive index (and θc)
When are sources coherent
Constant phase difference between them
What is a laser ?
Intense beam of monochromatic light
What makes light monochromatic ?
Single λ
Single frequency
Single colour
What are the dangers of laser light and precautions to be taken ?
Damage to eyes (intense energy at one point) :
- point at wall/floor and avoid reflective surfaces
What does an intensity-distance graph look like ?
Wave graph - each oscillation the peak gets smaller but same width apart
What happens in the double slit experiment ?
Light goes through a double slit and fringes are made from the light on screen
when does W = λD/s not work ?
When the angle between paths is big/D is not a lot bigger than s
What is diffraction ?
Bending of waves around an object
What happens in the single slit experiment ?
When using coherent light through a slit the light interferes with other light and creates fringes
What is diffraction grating ?
Sending light through many slits at once
