Simplified P1 - Wireless Signals & Stable Earth Flashcards
What are some examples of devices that use wireless technology?
Wireless technology is used by
- Radio & Television
- Laptops
- Mobile Phones
What happens to radio waves in earths atmosphere?
Radio waves are reflected and refracted in Earth’s atmosphere.
What can alter the amount of refraction?
The amount of refraction can be altered by the frequency of the waves, there is lower refraction at higher frequencies.
What can cause interference in radio stations?
Interference can occur in unusual weather conditions where the radio signals travel further and the broadcasts interfere.
How can you reduce interference in radio stations?
Interference in radio stations can be reduced through using digital signals.
Digital Audio Broadcasting, or DAB provides a greater range of Radio Stations however the Audio Quality is not as good as FM radio stations, but the Interference is completely eliminated.
What do radio waves do in Earth’s ionosphere?
Radio waves are reflected from the ionosphere, they would behave like light in an optical fibre and undergo total internal reflection.
What do radio waves do on water than they can not on land mass?
radio waves can be reflected by the water, but they can not be reflected by the land mass.
How can radio waves reach aerials not in its line of sight?
Radio waves being continuously reflected by the ionosphere and the ocean can allow the radio waves to be received by an aerial not in a clear line of sight.
What happens to Microwaves in the ionosphere?
Microwaves in the ionosphere can pass straight through.
What happens to a microwave once it passes through the ionosphere?
When a microwave passes through the ionosphere it can be received by orbiting satellites and be amplified, and transmitted back to Earth.
Where do communication satellites orbit?
Communication Satellites orbit above the equator and take 24 hours to orbit Earth.
What happens to Radio Waves when they meet an obstruction?
Radio waves are diffracted when they meet an obstruction.
What needs to be taken into account when transmitting signals to a satellite?
Refraction in the atmosphere needs to be taken into account when sending a signal to a satellite.
Why does the transmitting aerial need to send a focused beam?
The transmitting aerial needs to send a focused beam because the receiving aerial is very small.
How is energy lost when transmitting signals?
Some energy is lost form the edge of the transmitting aerial because of diffraction.
What is the purpose of a seismograph?
A seismograph shows the different types of earthquake wave
http://www.calvin.edu/academic/geology/seismology/Virginia%20Quake%208-23-2011.jpg
What do L waves do?
L waves travel round the surface very slowly.
What are P waves?
P waves are longitudinal pressure waves.
Where do P waves travel and how fast?
P waves travel through the Earth and they travel between 5 km/s and 8 km/s.
What materials can P waves pass through?
P waves can pass through Solids and Liquids.
What are S waves?
S waves are transverse waves.
What are transverse waves?
Transverse waves are a wave in which the vibrations are at a right angles to the direction of travel.
Where do S waves travel and how fast?
S waves travel through the Earth at speeds between 3 km/s and 5.5 km/s.
What materials can S waves pass through?
S waves can only pass through Solids.
What happens when P waves travel through the Earth?
When P waves travel through the Earth they are refracted by Earth’s core.
What can P waves help figure out?
P waves, when refracted by the Earth’s core allow scientists to work out the size of the Earth’s core due to the path the P waves take.
What happens to S waves when they pass through the Earth?
When S waves pass through the Earth they can not be detected on the other side, this is because S waves can not travel through liquids.
What information can S waves not being detected on the opposite side of Earth to an earthquake provide?
S waves not being detected on the opposite side of the Earth where an earthquake takes place allow scientists to deduce that the Earth’s core is liquid as S waves can not pass through it.
What causes a tan?
A tan is caused by the action of ultraviolet light on the skin.
What is melanin?
Melanin is a pigment that produces a tan.
What produces melanin?
Cells in the skin produce Melanin.
Why do people with darker skin not tan as easily?
People with darker skin do not tan as easily because the ultraviolet radiation is filtered out by the melanin, the darker the skin the greater the amount of melanin.
What is one way to reduce the chance of getting a tan?
Using sunscreen with a high SPF will reduce the risks of a tan and lower the chance of getting a tan.
What is the formula for the maximum length of time to spend in the sun?
Published normal burn time x SPF = Maximum length of time to spend in the sun.
Where is Ozone found?
Ozone is found in the stratosphere.
What does Ozone do?
Ozone in the stratosphere helps to filter out and absorb ultraviolet radiation.
What are CFCs doing to the ozone layer?
CFC gases from aerosols and fridges destroy ozone and reduce the thickness of the ozone layer.
– This increases the potential danger to humans
Where is the ozone layer thinnest in the world?
The ozone layer is at its thinnest above the South Pole because ozone depleting chemicals work best in cold conditions.
What do scientists use to monitor the thickness of the ozone layer?
Scientists are monitoring the thickness of the ozone layer using satellites.
