SCIENCE SEM 2 EXAM Flashcards
Electron Transfer
Sometimes electrons can be knocked off an atom or added to it, giving the atom an overall charge. The most common way an electron can be transferred is through rubbing one surface against another.
Static Electricity
Static electricity is the build-up of electric charge on a surface. This build-up most commonly occurs because one surface has rubbed off on another surface. Rubbing can cause electrons to be rubbed off on one surface, charging it positive.
AC (Alternating Current)
The current generated by electrons changing the direction in which they move
DC (Direct Current)
The current generated by electrons always moving in one direction
Voltage
A measure of the amount of energy provided to charges or used by them; measured in volts (V)
Current
The flow of charge
Insulators
A material that blocks current and heat e.g plastic, air, cloth, cork, wood and rubber
Conductors
A material that lets current and heat pass though e.g. glass and metal
Heat influencing the kinetic energy of particles
With an increase in temperature, the particles gain kinetic energy and move faster.
Convection
Transfer of heat in liquid or gas due to less dense, warmer matter rising and denser, cool matter falling e.g. heat spreading from an open fire through air in a room
Conduction
A method of heat transfer in which heat is passed by vibration of particles e.g. holding an ice block in your hand and you hand gets cold
Radiation
Movement of heat in the form of electromagnetic waves, which can travel through a vaccuum e.g. feeling the heat from the sun on your skin
Sound
Sound is produced when something vibrates, moving back and forth very quickly. Sound travels through vibrating particles. When something vibrates, it passes the vibrations into its surroundings e.g. air.
Sound Wave
Movement of alternating compression and rarefractions.
Transverse Waves
A wave in which the vibration is at right angles to the direction the wave is travelling.
Longitudinal Waves
A wave in which the vibration is in the same direction as the wave is travelling
Compression
A region of high pressure in which particles are close together
Rarefractions
A region of low pressure in which particles are far apart
Frequency
the number of waves passing a point for evry second
Transmission of sound through materials
Sound energy is transmitted through a material as longitudinal waves. The particles of the material vibrate as sound energy flows through. The more dense a material (more closely packed particles), the quicker sound travels. Therefore sound travels faster through solids than liquids and gases.
Reflection of sound
Hard surfaces (concrete or bathroom tiles) can reflect sound. This is called an echo.
Absorption of Sound
Soft materials (e.g. curtain fabric or carpet) can absorb sound energy and turn it into heat. This reduces ‘reverberation’ (how long a sound can be heard for).
Cochlear Implants
The cochlear implant mimics the way that the cochlea receives sounds. A microphone and speech processor are placed behind the ear. They pick up sounds and turn them into electrical signals.
Safe Sound Levels
Loudness is measured by decibels, and the higher the decibel is the louder the sound. Certain levels of sound can harm the human ears. Exposure to above 85dB can damage your hearing beyond repair.
Wegener’s Theory
Alfred Wegener proposed that the continents were once united into a single supercontinent named Pangaea. He suggested that Pangaea broke up long ago and that the continents then moved to their current positions. He called his hypothesis continental drift.
Sea-Floor Spreading
The process of new crust forming at the ocean ridges and spreading outwards
Hess’ Theory
50 years after Wegener proposed his theory, Harry Hess confirmed the theory by using the evidence of seafloor spreading to explain what moved continents.
Magnetic Stripping
Magnetic striping: the patterns of magnetism trapped in rocks on each side of plate boundaries. When molten rock solidifies, all its magnetic particles line up with Earth’s magnetic field to point in the same direction. The pattern of magnetism was symmetrical – the rocks at equal distances on each side of the ridge were formed at the same time and so had their magnetic fields pointing in the same direction. As Earth’s magnetic field changed over millions of years, so did the magnetic direction preserved in the rocks
Age of the Seafloor
The further the rocks of the Sea-floor were from the ridges, the older they were. The Sea-floor as very young compared with the rocks in the continents.
Sediment Thickness
The sediment rock layers on the ocean floor become thicker as you move away from the ridges. This means that sediments had been falling for longer on the rocks on the sea floor further away from the ridges
Volcano
Is a place where extremely hot material from inside Earth erupts at Earth’s surface. Materials can include:
Gas (Steam and hydrogen sulfide)
Ash
Lava
Lumps of solid volcanic rock such as scoria
Earthquake
Is the rapid movement of the ground, usually back and forth and up and down in a wave motion. Caused by the rapid release of energy as the tectonic plates move.
(Constructive) Divergent Plate Boundary
Where plates are moving away from each other in opposite directions. Aalso known as constructive boundaries. When the plates separate they leave a rift between them. The mid-ocean ridge forms a diverging boundary the ridge is the evidence that new curst is being constructed. Diverging boundaries also occur on land.
(Destructive) Converging Plate Boundary
Where plates are colliding with each other. They are also known as destructive boundaries. Rock is destroyed at converging boundaries. These collisions make all sorts of land features such as mountains, chains of island and underwater trenches.
Volcanoes and Plate Boundaries
Most volcanoes are found at or near plate boundaries. This is because the movement of the plates create weakness in the crust and also generates intense heat that can melt rock.
Earthquakes and Plate Boundaries
Most earthquakes start at the edge of a tectonic plate.
Transfer of Sound Energy regarding Aboriginal and Torres Strait Islander People
The traditional practice of clapping stones together under water to frighten fish closer to the surface for easier hunting has been documented throughout Australia. An interesting practice that provides evidence of this understanding is the driving of spears into sand under water to generate a specific signal for dolphins to assist in the mutual herding and hunting of mullet
How do light particles travel
Light travels as a wave. But unlike sound waves or water waves, it does not need any matter or material to carry its energy along. This means that light can travel through a vacuum—a completely airless space.
Properties of light
Frequency
Wavelength
Vaccuum
Frequency
The number of waves produced in each second
Wavelength
Distance between two successive waves and is usually measured in metres
Vaccuum
It is empty space in which light travels through
Law of Reflection
Angle of Incidence=Angle of Reflection
I=R
Refraction
The bending of light
Bionic Eye
The bionic eye is a device that consists of a camera attached to a pair of glasses. The bionic eye helps to enable a person to distinguish light from dark.
Electromagnetic Radiation
Consist of oscillating electric and magnetic fields travelling at the speed of light
Microwaves
Electromagnetic radiation with wavelengths ranging from fractions of a millimetre to tens of centimetres, used in communications and cooking
Analog Signals
A continuous signal that varies in amplitude or frequency with the information being transmitted.
Digital Signals
A signal consisting of a series of ‘on’ or ‘off’ pulses
Channels of Communication
Bandwith
Optical Fibre
Microwave links
X-Rays used in medicine
X-rays have great penetrating power and so are used to investigate the structure of objects and to find flaws in metals. X-rays are used in radiology, to produce images of bones. Ther are also used in radiotherapy, in which X-rays are targeted at cancer cells to kill them or stop them from multiplying.
Gamma Rays used in Medicine
Gamma rays have wavelengths of about one-hundered billionth of a metre. Gamma rays are useful in medical diagnosis. In positron emmision tomography (PET), a patient is injected with small amounts of radioactive material. the material emmits gamma rays, for a short period of time. The gamma rays are detected by a PET scanner or camera.
Sonar Technology in mapping the Sea-floor
Sonar technology such as GPlates helps scientist map the ocean floor.
Australian Continent Plate history
Australia was connected to the other continents forming together the supercontinent Pangea. ABout 40 million years ago, the south Tasman Rise separated, and Australia became an Island continent.
Incident Ray
The incoming ray of light
Reflected Ray
The ray that bounces off the mirror
Angle of Incidence
A right angle, known as ‘i’ on the surface of the mirror.
Angle of Reflection
A right angle, known as ‘r’ on the surface of the mirror.
Channel of communication-Bandwith
the ability to send information more quickly through a single communication channel.
Channels of Communication- Optical Fibres
In Australia from the late 1980s, a new network was laid next to the underground coaxial cable that linked cities. This network made from optical fibre. Optical fibres are thin, flexible tubes made of glass or plastic.
Channels of communication - Microwave Links
Microwaves signals are directed in short, straight-line paths. About 2000 phone conversations can be carried using a microwave system, with repeater towers required every 50km.
Channels of Communication- How do Optical Fibres work?
In an optical fibre transmission system, the signal is coded as a series of binary numbers. This signal is sent down the optical fibres as a series of millions of flashes of laser light.
