P4 - The nature and properties of waves Flashcards
Describe what waves do [1]
They transfer energy without transferring matter
What is a mechanical wave? [1]
A wave that needs a medium to travel through
What is a wavefront? [1]
A line on which the disturbance caused by waves has the same phase at all points (e.g. the crests of waves in a ripple tank)
Define frequency [2]
The number of waves per second / measured in hertz Hz
Define wavelength [1]
The same point on neighbouring waves
Define amplitude [1]
The maximum displacement caused by a wave
Describe waves that are in the same phase [2]
Waves that have the same speed and direction
Describe the motion of particles in a transverse wave and give an example [1]
Particles vibrate perpendicular to the direction of energy transfer / light
Describe the motion of particles in a longitudinal wave and give an example [1]
Particles vibrate parallel to the direction of energy transfer / sound
Recall the wave speed equation [1]
Wave speed = frequency x wavelength
Describe the law of reflection [1]
The angle of incidence = the angle of reflection
What causes refraction? [2]
A change in speed of the wave when it moves to a medium with a different density
What is diffraction? [1]
The spreading of waves at the edge of obstacles
What happens to a light ray that passes from a less dense medium to a more dense medium
It slows down / the ray bends towards the normal / angle of refraction is less than the angle of incidence
What is diverging light? [1]
Light rays spreading out
What is converging light? [1]
Light rays getting closer together
Define refractive index [1]
The ratio of the speeds of a wave in two different regions
Recall the equation for refractive index [1]
n = sin i / sin r
What is the critical angle? [1]
The angle of incidence where the refracted ray passes along the boundary between the two media
When does total internal reflection happen? [1]
When the angle of incidence is above the critical angle for a medium
What is total internal reflection used for? [1]]
Optical fibres in medicine and communication
Describe the action of a thin converging lens on a beam of light [1]
Bends light inwards
Define principle axis [1]
A line through the optical centre of a lens at right angles to the lens
Define principle focus (focal point) [1]
Point on a principle axis of a lens to which light rays parallel to the principal axis converge
