382558
Description
Flashcards by Anna Hollywood, updated more than 1 year ago
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Created by Anna Hollywood
almost 11 years ago
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| Question | Answer |
| What happens when energy flows from a warmer to a colder body? | The temperature of that object decreases |
| How does a thermogram show temperature change? | The hot end is white/yellow and the colder end is blue |
| What is the difference between temperature and heat? | Temperature is a measurement of hotness on an arbitrary scale and heat is a measurement of internal energy on an absolute scale |
| What is specific heat capacity? | The energy needed to raise the temperature of 1kg by 1 degree Celsius (measured in J/kg degrees Celsius) |
| What is specific latent heat? | The energy needed to melt or boil 1kg of the material (measured in J/kg) |
| Why when a material is changing state, energy is transferred, but the temperature stays the same? | The energy is just needed to break the bonds that hold the molecules together |
| How does double glazing reduce energy loss? | Through conduction as the particles in the gas are far apart so it's very difficult to transfer energy. |
| What are the 6 steps for how loft insulation helps reduce energy loss through conduction and convection? | Warm air in home rises. Energy is transferred through the ceiling via conduction. Air in the loft is warmed by the ceiling and is trapped in the loft insulation. No energy transferred as both sides of ceiling is same temperature. Without loft insulation, conduction can take place and the heat can get out via conduction. |
| How does cavity wall insulation help reduce energy loss by conduction and convection? | -Air in foam is good insulator -Air cannot move by convection as it's trapped in foam |
| How do insulation blocks wrapped in shiny foil help reduce energy transfer? | -Energy from sun is reflected back to keep the home cool in summer -Energy from home is reflected back to keep the home warm in winter |
| How does conduction work? | Due to transfer of K.E between particles |
| How does convection work? | Gas expands when heated making it less dense, so it rises. |
| How does radiation work? | Don't need a material to transfer energy, can be transferred through a vacuum |
| What can energy transformations be shown by? | Sankey diagrams |
| Payback time= | cost of insulation/annual saving |
| What are insulated buildings? | Energy efficient |
| What do designers and architects strive for? | The building to waste as little energy a possible |
| Define amplitude | The maximum displacement of a particle from its rest position |
| Define crest and trough | Crest-Highest point Trough-Lowest point |
| Define wavelength | Distance between two successive points on a wave having the same displacement and moving in the same direction |
| Define frequency | The number of complete waves passing a point in one second |
| Wave speed= | frequency x wavelength |
| What is the order of the electromagnetic spectrum? | Radio, microwave, infrared, visible, ultraviolet, x-ray, gamma ray |
| What has the longest wavelength in the electromagnetic spectrum? | Radio waves |
| What optical instruments use two or more plane mirrors? | A periscope |
| Why does refraction occur? | Because the speed of the waves decreases as the wave enters a more dense medium. The frequency stays the same but the wavelength changes |
| What is diffraction? | The spreading out of a wave as it passes through a gap |
| When does the most diffraction occur? | When the gap is about the same size as the wavelength |
| Where are diffraction effects most visible? | In telescopes and microscopes |
| How does Morse code work? What is it an example of? | It uses a series of dots and dashes to represent letters. It is an example of digital signal. |
| What signals are pretty much instantaneous? | Light, electricity, microwaves and radio waves. |
| What are the things to consider when thinking about the method of transmission? | -Can the signal be seen by others? -Can wires be cut? -How far does the signal have to travel? |
| What is the difference between white light and laser light? | White light is made up of different colours of different frequencies out of phase and laser light has only one frequency, is in phase and shows low divergence |
| How does laser light read the surface of a CD? | -CD surface is pitted -Pits represent the digital signal -Laser light is shone onto CD and the difference in reflection provides the information for the digital signal |
| When is the angle of refraction larger than the angle of incidence? | If the light is passing from a denser material into a less dense material |
| What is the angle of incidence called when the angle of refraction is 90 degrees? | The critical angle |
| What happens if the angle of incidence is bigger than the critical angle? | The light is reflected (total internal reflection) |
| How are telephone conversations and computer data sent? | Through optical fibres |
| Why are some fibres coated? | To improve reflection |
| How does an endoscope work? | The light passes along one set of optical fibres to illuminate the inside of the body, the light is reflected then the reflected light passes up another set of optical fibres to an eye piece/camera |
| What penetrates food more, microwaves or infrared? | Microwaves (1cm) |
| What other materials can microwaves penetrate, what's different with a microwave oven? | Glass or plastic but the glass used in a microwave oven reflects the wave back so they can't burn the body tissue |
| High/Low frequency short/long wavelength transfers the most energy | High frequency and short wavelength |
| How do normal ovens cook food using infrared? | -energy is absorbed by the surface of the food -K.E of surface food particles increases -rest of food heated by conduction |
| How do microwaves cook food? | Water and fat molecules vibrate more, increasing K.E and heating the rest of the food by conduction |
| What is the range of length of microwaves? | Between 1mm and 30cm |
| Why is less energy transferred using mobile phones? | Because they use longer wavelengths than in microwave ovens |
| What is used to communicate over long distances? | Microwave radiation |
| What must be in order for microwaves to be used? | Transmitter and receiver must be in line of sight |
| What else are used for microwave communication and how does this work? | Satellites. The signal from Earth is received, amplified and retransmitted back to Earth. No obstructions in space so they are in line of sight. Large aerials can handle thousands of phone calls and TV channels at once |
| What are there concerns about? | The use of mobile phones and where phone masts are positioned |
| Why can signal strength vary? (3 reasons) | -Microwaves don't diffract much -Weather and water can scatter signals -Curvature of earth limits line of sight |
| Why are mobiles banned on planes and in hospitals? | Because they can interfere with sensitive equipment. |
| What do infrared signals do? | Carry information that allows electrical devices to be controlled |
| What are the 3 main steps in how a TV remote works? | -Press button on remote completes the circuit and a coded signal is sent to LED on remote -Signal has start command, instruction command and stop command -LED transmits series of pulses which are received and decoded by device to do the command |
| What are the four improvements of the switchover from analogue to digital? | 1)Improved signal quality 2)Greater choice of programmes 3)Can interact with programme 4)Can get programme guides and subtitles |
| What do optical fibres allow? | Data to be transmitted very quickly using pulses of light |
| How do analogue signals work? | They are added to a carrier wave (CW freq usually higher) and the combined wave is transmitted. Interference from another wave can be added and transmitted. If the wave is amplified, so is the interference. |
| Why do interferences not show up on digital signals? | It only has two values |
| How does multiplexing work? | The different types of signals are put in a sequence then transmitted as one long sequence. The different signals are then reassembled at the other end. |
| Give 3 examples of where wireless technology is used | -Radio -Laptops -Mobiles |
| How are radio waves transmitted? | They are reflected and refracted in the Earth's atmosphere. There is less refraction at higher frequency waves |
| Do radio stations have there own particular frequency? | Yes |
| What can happen with radio waves? | Some radio stations can use the same frequency, although the waves are too far apart to interfere weather conditions can cause them to travel further and cause interference |
| How can we reduce interference? | By using digital signals |
| Why do people prefer DAB radios? | Although the audio quality isn't as good as FM signals, it eliminates interference between stations |
| Radio waves undergo... | ...total internal reflection |
| What reflects radio waves? | Water |
| What allows radio waves to be received by a receiver that isn't in line of sight? | The continual reflection between sea and the ionosphere |
| What type of wave can pass through the ionosphere? | Microwave |
| How long do communication satellites take to orbit the Earth? | 24 hours |
| What are the 5 problems with communication? | -Radio waves diffract when meeting an obstacle -Refraction in atmosphere needs to be taken into account -Beam needs to be focused as aerial is small -Some energy is lost from the edge of the T aerial (diffraction) |
| What are the 3 different types of waves shown on a seismograph during an earthquake? | -L waves -P waves (longitudal pressure) -S waves (transverse) |
| What are the 2 qualities of P waves? | -Travel through earth at 5-8km/s -Can pass through solids & liquids |
| What are the 2 qualities of S waves? | -Travel through earth at 3-5.5km/s -Can only pass through solids |
| What information have scientists gathered from P and S waves? | -P waves are refracted by core and paths taken by the wave tell scientists size of core -S waves won't travel through liquid, shows that core is liquid |
| What is tan caused by? | UV light, this causes production of melanin in skin (a pigment) |
| Why do people with darker skin not tan as easily? | UV light is filtered out |
| What is the equation to find out max length of time to spend in sun? | Published normal burn time x SPF of sunscreen |
| Why did scientists at first, not believe in the thinning of the ozone layer? | They thought there instruments were faulty |
| Where is ozone found? | In the stratosphere |
| What does ozone help do? | Filter out UV light |
| What destroys the ozone? | CFCs |
| Why is the ozone layer thinnest above the south pole? | CFCs work best in cold conditions |
| How do scientists monitor the thickness of the ozone layer? | Using satellites |
| What is there an international agreement to do? | Reduce use of CFC emissions |
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