Chapter 4 - Waves #1 Flashcards
What are mechanical waves?
Waves that travel through a medium.
i.e. oscillations of matter.
Electromagnetic waves are…
… oscillating electric and magnetic fields that pass through space without the need for a medium.
Electromagnetic waves include…
Radio waves, microwaves, infrared radiation, X-rays and gamma radiation
What are longitudinal waves?
Waves in which the direction of vibration of the particles is parallel to the direction in which the energy travels.
Longitudinal waves consist of regions of compression and rarefaction.
What are transverse waves?
Waves in which the direction of vibration is perpendicular to the direction in which the wave travels (direction of energy transfer).
What are plane-polarised waves?
Can longitudinal waves be polarised?
Transverse waves that vibrate in one plane only.
Longitudinal waves cannot be polarised.
What is the displacement of a vibrating particle?
Its distance and direction from its equilibrium position.
What is the amplitude of a wave?
The maximum displacement of a vibrating particle.
What is the wavelength of a wave?
The least distance between two vibrating particles with the same displacement and velocity at the same time. (e.g. distance between adjacent peaks).
One complete cycle of a wave is…
From the maximum displacement to the next maximum displacement. (e.g. from one wave peak to the next).
What is the period of a wave?
The time for one complete cycle to pass a fixed point.
What is the frequency of a wave?
The number of complete cycles passing a point per second.
What are the values for 1 cycle.
360°
2π
How do you calculate phase difference in radians?
λ
Give two examples of longitudinal waves.
Sound waves
Primary seismic waves
Give three examples of transverse waves.
Electromagnetic waves
Secondary seismic waves
Waves on a string
What is an oscillation?
A periodic vibration about an equilibrium.
If two points oscillating at the same _______ reach their maximum positive or negative displacement at the same time, they are said to _______ __ ______.
If two points oscillating at the same frequency reach their maximum positive or negative displacement at the same time, they are said to oscillate in phase.
If one point reaches maximum positive displacement as another reaches maximum negative displacement, the points ______ __ ________.
If one point reaches maximum positive displacement as another reaches maximum negative displacement, the points oscillate in antiphase.
If polarised light is passed through a polaroid filter that is perpendicular to the plane of polarisation of the polarised light…
…no light will get through.
Give 2 applications of polarisers.
- Polaroid material (e.g. sunglasses)
- Alignment of aerials for transmission and reception
What is the ‘direction of propagation’?
The direction in which a wave travels.
Polarisation is evidence that electromagnetic waves are…
…transverse
