Karteikarten
Ohne Titel
Karten in diesem Stapel (43)
- 1Relationship between angle of incidence and reflectionEqual
- 2Uses for ultrasound (>20 kHz)1. Prenatal scanning
2. Sonar - 3Speed of EM waves in a vacuum3 x 10^8 ms-1
- 4Order of EM waves Descending wavelength Ascending frequencyRadio Waves
Microwaves
Infrared
Visible Light
Ultraviolet
X-Rays
Gamma Rays - 5How radio waves are used in communication1. Long radio waves diffract around the Earth's curved surface, hills and tunnels
2. Allows radio signals to be received even if transmitter isn't in line of sight of transmitter
3. Short radio waves used for TV and FM radio
4. To get reception, you must be in line of sight of transmitter
5. Short radio waves can also be received long distances as they can be reflected from the Earth's ionosphere - 6Uses of microwaves1. Satellites
- Signal transmitted to space, picked up by satellite, transmits signal in different direction, received by ground satellite
*slight time delay between transmitted and received microwaves due to long distance traveled
2. Mobile phones-microwaves travel from your phone to nearest transmitter
3. Microwaves- shorter wavelength so can be absorbed by water molecules - 7Health risks of microwaves1. Phones- microwave could heat body tissue and cause cells to be burned or killed
2. Thought that using mobile phones or living near mobile phone mast could damage your health
3. No conclusive proof - 8How infrared radiation can be used to monitor temperature1. Heat radiation
2. More IR radiated for hotter objects
3. Detected by IR sensors
4. Night vision converts IR into electrical signals displayed on a screen - 9Uses for infrared radiation1. Cooking (grills, toasters)
2. Transmit information over short distances (mobile phones and computers)
3. Remote controls
4. Optical fibres - 10Optical fibres1. Carries data over long distances quickly (used in phone lines)
2. Uses IR and visible light
3. Signal carried as pulses of light and is reflected off the sides of a very narrow core from one end of the fibre to the other - 11Dangers of infrared radiation1. When radiation is emitted back from the surface of the Earth to the Sun, it is at a lower frequency, IR
2. IR is absorbed by atmospheric gases
3. Gases reradiate heat in all directions, including back to Earth
4. Contributes to global warming (greenhouse effect)
5. Can also cause skin burns - 12Uses of visible light1. Sight
2. Cameras - 13Uses of ultraviolet radiation1. Fluorescence is when chemicals absorb UV and emit visible light
2. Used to detect fake bank notes
3. Security pens
3. Fluorescent lamps - 14Dangers of ultraviolet radiation1. Prolonged exposure to sunlight
2. Increased chance of getting skin cancer
3. UV damages DNA in skin cells
4. Can cause eye problems (cataracts), and premature aging - 15What EM waves are ionising radiation?1. Ultraviolet radiation
2. X-Rays
3. Gamma radiation - 16Uses of X-Rays and dangers1. Used in hospitals, to identify broken bones
2. Pass easily through flesh but not through desnser materials like bones
3. Amount of radiation absorbed forms the image
4. Security use X-Rays to scan luggage and suspicious items
* Can cause cancer so lead aprons and screens are used in hospitals, or the room is evcuated before use - 17Uses of gamma rays and dangers1. High doses can be used to treat cancers
2. Used to diagnose cancers
3. Radioactive isotope injected into patients
4. Gamma camera detects where isotope travels in the body
5. Creates image which can be used to detect where cancer may occur - 18Explain the build up of static electricity by friction1. Electrons are negatively charged
2. Two insulating materials are rubbed together
3. One is oxidised, one is reduced
4. Polythene rod is reduced when rubbed with a cloth duster
5. Acetate rod is oxidised when rubbed with cloth duster - 19Dangers of static electricity1. A lot of charge can build up on synthetic clothes- eventually a potential spark could form
2. Grain chutes, paper rollers and fuel filler pipes generate static electricity build up. This could lead to a spark- dangerous when filling up car with fuel
3. Objects can be earthed or insulated to prevent sparks - 20Uses of static electricity1. Paint sprayers to give an even coating
-spray gun charged so each drop of paint repel eachother
- Object being painted is given opposite charge
2. Dust precipitators to clean up emissions from factories and power stations
-dust particles pass through a negatively charged wire grid in the chimney
- dust particles are attracted to metal plates and fall to be collected
3. Defibrilators give electric shocks
- two paddles, connected to power supply, placed on chest
- insulated handles, only patient shocked
- charge passes through paddles to make patients heart contract - 21Define electromagnetic inductionGeneration of a potential difference across as conductor which is experiencing a change in magnetic field
- 22Describe electromagnetic induction with a magnet and a coil of wire1. Move a magnet in a coil of wire or moving an electric conductor in a magnetic field
2. Shifting the magnet generates a current
3. Moving the magnet in the opposite direction, or reversing the polarity, reverses the potential difference/ current
4. Moving the current back and forth produces a potential difference that alternates direction (AC) - 23Describe how turning a magnet, end to end, in a coil generates current1. Turning the magnet changes the magnetic field through the coil, inducing a potential difference- making current flow
2. A half turn reverses the direction of magnetic field and potential difference, current flows in opposite direction
3. Continuously turning in the same direction produces an AC current - 24Factors affecting the size of induced voltage1. Strength of magnetic field
2. Cross sectional area of the coil
3. Number of turns of the coil
4. Speed of movement
Increasing on or more of these factors, increases voltage - 25Role of step up and step down transformers1. Step up
Increase voltage, decrease current
2. Step down
Decrease voltage, increase current - 26How transformers work1. AC current generated
2. Primary coil produces magnetic field which remains in iron core- nearly all passes through secondaryv coil
3. Changing magnetic field induces an alternating voltage across the secondary coil - 27PowerP= I x V = (I^2) x R = (V^2)/ R
- 28What is resistance proportional to?1. Directly proportional to the length of the wire
2. Inversely proportional to the cross sectional area of the wire - 29Deflection of ionising radiation1. Alpha and beta particles are charged so get deflected by electric and magnetic fields
2. Gamma radiation is a wave with no charge so doesn't get deflected - 30Existence and origin of background radiation1. Radioactivity naturally occurs in unstable isotopes (most background radiation occurs in natural resources)
2. Cosmic rays
3. Human activity- nuclear explosion fallout, hospital or industry waste (small proportion) - 31Order ionising radiation Descending ionising power Ascending penetration powerAlpha particles
Beta particles
Gamma Rays - 32Materials that can block radiation1. Alpha- paper
2. Beta- thin aluminium
3. Gamma- thick lead - 33What is radiation dose measured in?Sieverts (Sv) or millisieverts (mSv)
- 34Unit of radioactivityBecquerel (Bq)
One nucleus decaying per second - 35Define half lifeAverage time for the number of unstable nuclei in a radioactive isotope sample to halve
- 36How to calculate half life1. Subtract background count rate
2. Deduce the number of half lives within the time period given
3. Divide the time given by the number of half lives, to find the half life - 37Uses of radiation1. Alpha- smoke detectors
2. Beta- medical tracers, thickness gauges
3. Gamma- medical tracers, treatment of cancer, sterilisation of food and surgical equipment - 38Isotopes used in nuclear fissionUranium-235
(sometimes plutonium -239) - 39Describe the chain reaction for the nuclear fission of uranium-2351. Slow moving neutron absorbed into uranium nucleus, making the nucleus unstable-causing it to split
2. When the uranium nucleus splits, it releases 2 or 3 more neutrons, which may hit other nuclei
3. The chain reaction is continued
4. Control rods absorb some of the neutrons and slow down the reaction- they can be moved further in or out of the reactor
5. When the atom splits, two new smaller nuclei are formed- usually radioactive as they have the incorrect number of neutrons
6. Nuclear fission releases a lot more energy than chemical reactions - 40Equation for the nuclear fission of uranium-235
- 41Outline nuclear fusion1. Smaller nuclei joining to make a larger one, commonly 2 different hydrogen isotopes form helium
2. Useful fusion reactions produce more energy than fision reactions
4. Requires really high temperature and pressures
5. No material can withstand high temperatures and pressures needed so fusion reactors are hard to build - 42Uses of nuclear fusion1. Energy source
2. Fusion (hydrogen) bombs
- fission reaction creates high temperature
-fusion reaction causes explosion - 43Describe the Doppler effect1. Source moving towards you will seem to have higher frequency and shorter wavelength
2. Source moving away from you will seem to have a shorter frequency and longer wavelength
3. Objects moving away will be more redshifted
Objects moving closer will be more blue shifted
Informationen
- Beschreibung
- Entrance Exam BMAT Karteikarten am Ohne Titel, erstellt von Andrei De Leon am 28/10/2018.
- Erstellt von
- Andrei De Leon · Okt 2018
- Aktualisiert
- 29 Okt 2018
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