waves

transfers energy without transferring matter

vibrations are in the same direction as the travel of the energy

Vibrations are at 90° to the direction energy is transferred
amplitude in meters

Amplitude: the height of the wave from rest to crest
Wave length: The distance from any point on a wave to the same point on the next wave.
period (T) in seconds

Period: the time taken for one complete wave to pass a point
Frequency: number of waves that pass a single point per second

wave speed = frequency × wavelength
v = f × λ

Frequency = 1/Time period
F = 1/T

The complete range of electromagnetic waves placed in order of increasing frequency and decreasing wavelength
Radio waves, microwaves, infrared radiation, visible light (ROYGBIV), ultraviolet, X rays, gamma rays

Allll are transverse - travel in same speed in a vaccum (300,000 m/s) - All transfer energy - All can be reflected and refracted

When light hits a surface and bounces off

wave hits the boundary face on it slows down but carries on in the same direction
wave meets a different medium at an angle the direction and speed changes. If light enters a more dense material - refracted ray bends towards the normal and the angle of refraction is smaller than angle of incidence. If light enters a less dense object the ray bends away from the normal.

radio waves: broadcasting and communications microwaves: cooking and satellite transmissions
infrared: heaters and night vision equipment
visible light: optical fibres and photography

ultraviolet: fluorescent lamps
x-rays: observing the internal structure of objects and materials, including for medical applications
gamma rays: sterilising food and medical equipment

microwaves: internal heating of body tissue
infrared: skin burns
ultraviolet: damage to surface cells and blindness
(sunscreen with UV filters and sunglasses for overexposure)
X rays and gamma rays: are ionising - cancer, mutation (minimal exposure, protective lead shielding)

An observed change in the frequency of a wave when the source or observer is moving. IF the wave source is moving towards the observer the wave length decreases and frequency increases as the waves are compressed. oppposite when it is moving away from the observer. Ambulance - high pitched when moving towards you

Angle of Incidence = Angle of Reflection

The imaginary line drawn perpendicular to the surface of a mirror or any surface.
Angle of incidence (i)

i: The angle formed by the incident ray and the normal.
r: The angle between the reflected ray and the normal.

when the speed and direction of a wave changes when in enters a different density material

The angle between the refracted ray and the normal.
Snell's Law

n = sin(i) / sin(r)

tells how fast light travels in that material. light slows down when it enters the material - high refractive index. Air refractive index is 1

- Draw around a rectangular glass block on a piece of paper and direct a ray of light at an angle
- Trace the incident and emergent ray onto the paper
- remove the block and draw refracted ray in between
- draw the normal at 90 degree - measure < of i and < of r then caclulate refractive index

when light reflects back into the material

The angle of incidence at which the refracted ray is perpendicular to the normal.

sin C = 1/n

Optical fibres - light always enters at an angle creater than critical angle so all the light is toatally internally reflected
Periscopes - using prisms to see objects that are not in line of site, ray of light travels into one prism where it is totally internally reflection by 90, then travels to another prism and totally reflected again

frequency range for human hearing
20-20 000 Hz

Greater amplitude - louder
Higher frequency - higher pitch