C11 Waves 1 Flashcards
Define Progressive Wave
An oscillation that travels through a medium, transferring energy from one point to another, without permanently displacing any matter.
Define Transverse Wave, giving example
- A wave in which the oscillations or vibrations are perpendicular to the direction of energy transfer.
- S-waves, EM waves, water waves
Define Longitudinal Wave, giving example
- A wave in which the oscillations or vibrations are parallel to the direction of energy transfer.
- Often called compression waves, they are made of compressions and rarefactions.
- Regions of higher pressure and lower pressure air move, not particles.
- P-waves, sound waves
Formula of intensity of a wave
Radiant Power / Surface Area
I = P / A
What is phase difference
The difference between the displacement of particles along a wave, measured in degrees (360°) or radians (2π)
Antiphase
A phase difference of 180°, or π, where the max positive displacement of one wave is the max negative displacement of another.
What is reflection
A wave changes direction at a boundary between two different media, remaining in the original medium.
What is refraction
- A wave changes direction as it passes from one medium to another.
- There is always partial reflection when a wave refracts.
When do water waves refract, and what happens in shallower water.
- When there is a change in depth.
- When entering shallower water, waves slow down and wavelength shortens.
Why are optical microscope limited at a few hundred nanometres?
The diffraction of light as they pass through the apertures in the microscope cannot be avoided at a distance that small.
What affects how much diffraction occurs? When is it at its maximum?
- The relative sizes of the wavelength and the gap through which the wave passes through.
- The effect is strongest when the wavelength of the wave is roughly the same size as the gap.
What is partial polarisation
- It is when transverse waves reflect off a surface, e.g. light on water.
- There are more waves oscillating in one particular plane, with the water example it is horizontal polarisation.
Formula for intensity relating distance
I = P / 4πr^2
That is the surface area of a sphere, as the waves travels outward in all directions like a sphere.
Relationship between intensity and amplitude
Intensity is directly proportional to the amplitude^2
What is an EM wave?
Transverse waves, which can be thought of as electric and magnetic fields oscillating at right angles to each other.
