yr 9 physics

vacuum

sound cannot travel through this

Microwave

Electromagnetic waves that have shorter wavelengths and higher frequencies than radio waves.

x-rays

form of em radiation, with high energy and short wavelength

closed switch

allows current to flow

Parallel circuit

When components are connected in branches adjacent to one another.

Insulator

A material that does not conduct electricity.

Resistance

A measure of how difficult it is for current to pass.

Measured in ohms (Ω).

Ohms

Unit for resistance

Fuse

A wire of high resistance; it will melt if too much current flows in the circuit.

decibel

unit used to measure amplitude

matter

sound requires this to be transmitted

Conduction

The transfer of heat between substances that are in direct contact.

Convection

the transfer of heat in liquids/gases where warmer portions of the fluid rise, while cooler, more dense portions sink.

Non-luminous

An object that does not release or emit light.

Shadow

A dark area where light from a light source is blocked by an opaque object.

Violet

High frequency / high wavelength light waves.

Transverse (electromagnetic) wave

Light is this type of wave.

Regular reflection

When light reflects off a smooth surface (such as a glass or a window) it produces a clear reflected image.

Angle of incidence

The angle an incoming ray makes with the "normal".

Angle of reflection

the angle a reflected ray makes with the "normal".

Concave mirror

Mirror that causes light rays to point inwards. This can produce an upright and diminished image as well as an inverted magnified image depending on distance.

Virtual image

Image that appears in a mirror

Reflection

When light bounces off a surface at an angle relative to the angle of incidence.

White Light

This light is a mixture of many different colours, each with a different frequency.

Dispersion

When white light passes through a prism, each individual frequency of light is bent, or refracted, a slightly different amount.

Polarisation

Light waves in which the vibrations occur in a single plane.

Infrared

Electromagnetic waves of frequencies lower than the red of visible light.

Uses for microwaves

Heating food in a microwave oven or transmitting information from one place to another.

Uses for x-ray

primarily used for medical imaging as it can penetrate substances such as skin and muscle (eg. diagnostic radiography)

Red

Longest wavelength of visible light

amplitude

total distance a wave moves up and down from its resting position

wavelength

distance from any point on one wave to a corresponding point on the next wave, such as crest to crest or trough to trough

transverse wave

a wave that moves perpendicular (up and down) to the direction that it travels

Period

The time for one complete cycle of a wave.

ammeter

An instrument that measures current.

Conductor

A material that allows a current to pass through it.

transverse wave

a wave in which the vibration is at right angles to the direction the wave is travelling.

wavelength

the distance from one peak to the next or one compression to the next.

compression

a region of high pressure where particles are close together.

echo

a sound that is reflected and heard a second time

frequency

the number of waves passing a point every second

Hertz

the unit used to measure frequency

longitudinal wave

a wave in which the vibration is in the same direction that the wave is travelling

rarefraction

a region of low pressure, in which particles are far apart.

sound wave

regions of high and low pressure originating from a vibrating object and transmitted through a medium.

pitch

the way we hear frequency

(measured in Hertz).

vibration

how sound is created

wave

transfer energy without a transfer of matter

metres

units used to measure wavelength

solids

the medium in which sound travels fastest

gases

the medium in which sound travels slowest

Radiation

The transfer of heat through a vacuum and to an object by electromagnetic waves.

White

Colour that reflects most radiation.

Black

Colour that absorbs most radiation.

Insulator

A poor heat conductor, heat energy does NOT pass through it easily.

Heat

The transfer of energy.

Thermal Energy

The total energy of all the particles within an object.

Joules

Units used to measure heat.

Hot to cold

Heat is always transferred in this direction.

Thermometer

Device used to measure temperature.

Degrees Celsius

Units used to measure temperature.

Temperature

Average energy of all particle within an object (°C).

Metal

Example of a good conductor of heat.

Plastic, wood

Examples of bad heat conductors

Luminous

An object that releases or emits light.

Opaque

When light is either reflected or absorbed into the substance.

Translucent

Some light is reflected. Some light passes through but it is scattered.

Transparent

Almost all light is transmitted through this substance.

Speed of Light

300,000,000 meters per second

Electromagnetic wave

Light wave consisting of alternating electric and magnetic fields. This can also be described as a transverse wave.

Colour

The way we see the frequency of the light waves.

Red

Low frequency / low wavelength light waves.

Diffused Reflection

Although they may appear smooth, the surfaces of most objects are rough close up. These surfaces reflect light in many directions and do not form an image.

Normal

An imaginary line that is drawn at right angles to a surface that a light is hitting (incident on).

Law of reflection

The angle of incidence is always equal to the angle of reflection (incidence = reflection).

Plane mirror

Mirror that produced an upright, laterally inverted virtual image.

Convex mirror

Mirror that causes light rays to radiate outwards, resulting in an upright and diminished image.

Real image

Image that appears in the real world. Concave mirrors in projectors create images.

Refraction

The bending of light as it enters or leaves different substances at an angle.

Depth Illusion

The bending of light rays from air to water can make objects appear closer than they really are.

Visible Light

A portion of the electromagnetic spectrum that is visible to the human eye.

White

Reflects all the colours and the radiant heat.

Black

Absorbs all the colours and the radiant heat.

Scattering

When a beam of light is redirected in many different directions as it interacts with a particle of matter.

Additive colour

Filters red, green & blue of light.

Subtractive colour

Pigments red, yellow & blue of paint.

Filter

Transparent materials that only allow light of a particular colour to be transmitted.

Radio Wave

Electromagnetic waves with the longest wavelengths and lowest frequencies

Visible light

Electromagnetic radiation that can be seen with the unaided eye

Ultraviolet radiation

Electromagnetic waves with wavelengths that are shorter than visible light but longer than X-rays.

Gamma rays

Electromagnetic waves with the shortest wavelengths and highest frequencies.

Uses for radiowaves

Transport information through the atmosphere without wires.

Uses for infrared radiation

Night vision goggles, thermal imaging and remote controls.

Uses for ultraviolet radiation

UV lasers, fluorescent lamps and disinfecting waste water, identifying fraudulent bank notes. Too much exposure can cause sunburn.

Uses for gamma rays

Kills living cells, such as cancer, but can provoke DNA alteration by interfering with genetic material.

Violet

Shortest wavelength of visible light

frequency

the number of waves per second

Hertz

The unit used to measure frequency

wave

the transfer of energy without the transfer of matter

longitudinal wave

a wave that moves back and forth parallel to the direction that it is traveling