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- 1What do lasers produce? -Lasers produce narrow intense beams of monochromatic light.What is the same in a laser beam?
All the waves are at the same frequency and wavelength this is what makes the light monochromatic. - 2What does Low divergance mean? The beam is narrow and it stays narrow even at a long distance from the light source.Give an example of an object with low divergance and an pbject with high divergance.
A torch- High
A laser- Low - 3Describe the surface of a CD. It has a pattern of billions of shallow pits cut into it. The areas between the pits are called lands.Name four jobs that lasers can be used in.
-Manufacturing
-Surgery
-Dentistry
-Weapons - 4What is Infrared radiation? IR is also known as heat radiation, Its given out by hot objects. This means IR can be used to monitor temperatures. For example police us this to catch criminals.Name five uses of infrared radiation.
-Cooking
-Remote Controls
-Mobile phones/Computers
-Secturity systems
-Optical fibres. - 5What are Radio waves used for? Radio waves are used for broadcasting radio and TV programmes. Anyone with a receiver can tune it to the radio frequency to pick up the signal.Where must mircowave sources be for the best signal?
Must be in line of sight, so they are positioned high up, often on tall masts, close together so that hills, or the curvature of the Earth, cannot block the beam. - 6Why might mircowaves be sent to a satilite first? If needed to travel very very far distences then the waves have to go to the satilite first then be bounced back out. This could be for phone calls or Tv shows.What is Diffraction?
Diffraction is the spreading of a beam through gaps and around corners. The maximum effect occurs when the gap has a similar size to the wavelength. - 7Describe what an Analogue signal looks like.Describe what a digital signal looks like.
- 8What type of wave does a mobile phone use? Mircrowave.Why are digital signals better than analogue signals?
They can be cleaned up in a process known as regeneration because each pulse must be a 0 or a 1, so other values can be removed. Analogue signals can be amplified, but the noise is amplified too. - 9List the electromagnetic spectrum from highest engery to lowest. Gamma, X-ray, Ultraviolet, Visible, Infrared, Microwave, Radio wavesWhat frequency does a wave have if its wavelength is long?
A low frequency - 10Which form of radiation is the most dangerous? GammaWhat is the speed of light in a vaccum?
3 x 10^8 m/s - 11What is the equation for wavespeed? Wavespeed= Frequency x Wavelength.Give two reasons for why Global warming is happening.
-Fossil fuels are being burned/Combusted
-Forests are being destroyed meaning less trees are using C02 for photosynthesis. - 12Give three effects global warming might have. -Extreme weather conditions. -Rising sea levels due to melting ice -No longer able to grow food crops.What three things does UV rays cause?
-Sunburn.
-Skin cancer.
-Cataracts. - 13Name the three ways heat can be transferred. -Conduction. -Convection. -Radiation.Explain conduction.
In a hot solid, particles vibrate more. They collide with the particles next to them and set them vibrating. The kinetic energy is transferred from particle to particle. - 14Why are metals much better at conducting than other materials? Because metals have free electrons to give up easily meaning they will let them go and pass them along, conducting the electricity.Explain convection.
In a hot fluid , particles have more kinetic energy so they move more. They spread out and the fluid becomes less dense. The hot fluid rises above the denser cold fluid forming a convection current. - 15Explain Radiation. All objects emit and absorb infrared radiation. The higher the temperature the more they emit. When objects absorb this energy their temperature increases.Explain Double Glazing.
Double glazing is when windows have a piece of glass then a gap of air then a piece of glass. This gap of air traps the escaping heat and reduces the amount of heat wasted from the house. - 16What are the three main greenhouse gases? -Water Vapour. -Carbon Dioxide. -Methane.Why doesnt UV rays give cancer to everyone?
UV radiation from the Sun reaches the surface of the Earth but the highest energy ultraviolet radiation is stopped by the ozone layer. This prevents everyone becoming affected by its dangerous rays. - 17What do some scientist believe caused the hole in the Ozone layer? -CFC's from Areosol cans. -Refrigerant in refrigerators and freezersWhy is infrared radiation used for cooking food?
When Infrared radiation it is absorbed, all the particles in the surface are heated. Anything that is touched by IR feels heat so it is most effective when heating food.
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- Year 11 Science Fichas sobre Sin título, creado por Josie Wright el 17/05/2017.
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- Josie Wright
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