Paper 1-Waves Flashcards
What is a transverse wave?
A wave in which particles oscillate perpendicular to the direction of energy propagation
What is a longitudinal wave?
A wave in which the particle oscillate parallel to the direction of energy transfer
Define time period
The time taken for one complete oscillation
Define frequency
The number of waves that pass a specific point per second
Define wavelength
The distance between one peak and the next
Define amplitude of a wave
The maximum displacement of a particle from its equilibrium position
Can longitudinal waves be polarised?
No
What is polarisation?
Allowing the wave to travel in one plane only
Why must TV aerials be correctly aligned?
Incident radio waves are polarised so ariel must be aligned in the same plane for maximum absorption
State and explain one use of a polarising filter
Sunglasses
To reduce the intensity of light to the eyes by reducing the amount of waves that can pass through the lens
How far apart are waves in antiphase?
180 degrees or pi
What is the principle of superposition?
The resultant displacement caused by two waves arriving at a point is the vector sum of the displacements caused by each wave at that instant
Other than electromagnetic waves, give one example of a transverse wave
Waves on a string
How is stationary wave formed?
The wave is reflected and superposes, creating nodes and antinodes
How many minima are there in 1 wavelength?
3
What is the refractive index of air?
1
What are the 2 main functions of the cladding in an optical fibre?
Protect the inner core from scratches
Prevent light escaping to adjacent fibres
What is the critical angle?
The angle of incidence at which the angle of refraction in 90 degrees
When does total internal reflection occur? (2 points)
When the angle of incidence is greater than the critical angle
When light is travelling from a more dense medium into a less dense medium.
Give 2 uses of fibre optics
Broadband communications
Endoscopes in hospital
Does the cladding of an optical fibre have a higher or lower refractive index than the core and why?
Lower to allow total internal reflection to occur
What are the 2 causes of signal degradation in an optical fibre?
Absorption and dispersion
Describe how absorption causes signal degradation in an optical fibre
Some rays are absorbed by the fibre, causing the amplitude of the signal to decrease
Describe how modal dispersion causes signal degradation in an optical fibre
Rays enter the fibre at different angles, so take different paths of different lengths. They arrive at different times, causing pulse broadening
