Waves and the Electromagnetic Spectrum

Flashcards generated from lecture notes on Waves, the Electromagnetic Spectrum and other wave phenomena.

Wave Energy Transfer

Waves transfer energy without the overall transfer of matter.

Wavelength (λ)

The distance from one point on a wave to the identical point on the next wave (peak to peak), measured in meters (m).

Amplitude

Half the height from peak to trough, or the height measured from the center line to the peak.

Frequency (f)

The number of waves that pass a point each second, measured in Hertz (Hz).

Time Period (T)

The time for one complete wave to pass a point, measured in seconds (s).

Relationship between Time Period and Frequency

T = 1/f

Wave Equation

v = fλ

Electromagnetic (EM) Spectrum

A group of waves that all travel through a vacuum and at the speed of light.

Order of EM Spectrum

Radio, Micro, Infra-red, Visible light, Ultra violet, X-rays, Gamma rays

Uses of Radio Waves

Used for terrestrial TV, radar, Wi-Fi, and Bluetooth; produced by electrons vibrating at the frequency of the wave.

Uses of Microwaves

Used in microwave ovens (heats water molecules in food), mobile phones, satellite TV, and satnav (GPS).

Uses of Infra-red

Used in grills, toasters, radiant heaters, remote controls, security cameras/sensors, night vision goggles, and fibre optic cables.

Uses of Visible Light

Used in fibre optic cables, optical microscopes, seeing things (illumination), cameras, and lasers.

Uses of Ultra Violet

Used in invisible ink, setting glue/nail varnish, and sun beds.

Uses of X-rays

Used for taking pictures of bones and checking machines for cracks; are created by stopping fast moving electrons.

Uses of Gamma Rays

Used for sterilizing food or surgical implements, killing cancerous cells, checking welds, and radioactive tracers; created by some naturally occurring materials.

Law of Reflection

Angle of incidence = angle of reflection.

Refraction as Light Enters a Denser Medium

Light slows down and bends towards the normal.

Refraction as Light Exits a Denser Medium

Light speeds up and bends away from the normal.

Ultrasound

Any sound above 20,000Hz.

P-waves (Seismic)

Longitudinal; travel through solids and liquids.

S-waves (Seismic)

Transverse; travel through solids, but NOT liquids.

Determining Distance to Objects

Determined by reflecting waves off them using sound waves (SONAR) or radio waves (RADAR)

Convex Lenses (Converging)

Bend rays of light that are parallel to the optical axis inwards, so that they cross at the focal point (f).

Concave lenses (Diverging)

Spread out rays of light that are parallel to the optical axis, in such a way that they appear to come from the focal point.

Magnification Equation

image height / object height or image distance / object distance

Primary Colors of Light

Red, blue and green

Secondary Colors of Light

Magenta, yellow and cyan

Black Body

A perfect absorber and emitter of radiation.