Light + Sound

Light

Visible electromagnetic radiation

Luminous

Object that emits light

Waves

Oscillating motion

Rays

Light waves travelling in straight paths

Shadow

Absence of light behind an object

Opaque

Object through which light cannot be transmitted

Umbra

Area in shadow (during an eclipse)

Non-luminous

Object that does not emit light

Transmit

Allows through

Reflected

Bounced off

Absorbed

Taken in

Transparent

Allows all light through

Translucent

Allows some light through

Plane mirror

Flat and smooth reflective surface

Image

Appearance of an object in a mirror

Angle of incidence

Measured between the normal and incident ray

Normal

'Imaginary' line at right angles to a reflective surface

Angle of reflection

Measured between the normal and reflected ray

Refraction

Change in direction as light moves into a different medium

Total internal reflection

Reflection within an object (when angle of incidence is greater than the critical angle)

Optical fibre

Material that sends information using light

Endoscope

Medical imaging device that uses optical fibres

Critical angle

Angle above which light reflects (instead of refracting) within a material

Disperses

Breaks off in different directions

Spectrum

Range of wavelengths (and colours)

Wavelength

Distance between two peaks in a wave

Rainbow

Caused by dispersion of light in water droplets

Eye

Sense organ of light

Cornea

Transparent layer at front of the eye

Lens

Object that focuses light

Retina

Light sensitive region at back of the eye

Rods

Cells that detect light and dark

Cones

Cells that detect colour

Optic nerve

Connection between eye and brain

Colour blindness

Genetic disease - prevents people from distinguishing between colours

Laser

Device that amplifies light waves

Vibration

Movement of material back and forth

Compression

High density areas of molecules in sound waves

Rarefaction

Low density areas of molecules in sound waves

Eardrum

Part of the ear - transmits sound waves to the hammer bone

Decibel (dB)

Unit of measurement for volume

Frequency

Number of waves passing in a given time

Hertz (Hz)

Unit of frequency (1 wave per second)

Pitch

How high or low a sound is

Audible

Able to be heard

Echo

Reflection of a sound wave

Ultrasound

Frequencies above human hearing

Sonar

Device using ultrasound to detect objects

Oscilloscope

Device used to visualise sound waves

Supersonic

Faster than Mach 1