OCR GATEWAY PHYSICS P1

• HEAT - MEASURE OF KINETIC ENERGY (PARTICLES MOVE MORE WHEN HEATED - ABSOLUTE SCALE (CAN'T < 0)
• TEMPERATURE - MEASURE OF HOTNESS - AVERAGE KINETIC ENERGY OF PARTICLES IN SUBSTANCE - MORE HEAT SOMETHING HAS, THE HIGHER THE TEMPERATURE, THE HIGHER THE AVERAGE KINETIC ENERGY - MEASURED IN DEGREES CELCIUS - NOT ABSOLUTE (CAN GO BELOW ZERO)

MOVEMENT OF HEAT

• IF THERE IS A DIFFERENCE IN TEMPERATURE BETWEEN TWO PLACES, ENERGY WILL FLOW BETWEEN THEM.
• THE GREATER THE DIFFERENCE IN TEMPERATURES, THE FASTER THE RATE OF COOLING WILL BE, AS HEAT WILL ATTEMPT TO EVEN OUT THE TWO TEMPERATURES BY MOVING FROM THE HOTTER PLACE TO THE COOLER PLACE

THERMOGRAMS - REPRESENT TEMPERATURES BY SHOWING OBJECTS AS A RANGE OF COLOURS

•  COLOURS DEPEND ON HOW MUCH INFARED RADIATION IS DETECTED
• RED/YELLOW - HOTTEST PARTS            
• BLACK/DARK BLUE/PURPLE - COLDEST PARTS

MELTING AND BOILING

•  BOILING - WHEN A LIQUID IS HEATED, THE KINETIC ENERGY MAKES PARTICLES MOVE FASTER, EVENTUALLY CAUSING THE PARTICLES TO OVERCOME THEIR ATTRACTION TO EACHOTHER, SPREADING OUT AND BECOMING A GAS. 
• MELTING - WHEN A SOLID IS HEATED AND THE PARTICLES VIBRATE FASTER, THEY TOO OVERCOME THEIR ATTRACTION TO EACHOTHER AND BECOME A LIQUID
• WHEN A SUBSTANCE IS MELTING OR BOILING, ENERGY IS STILL BEING PUT IN BUT IS BEING USED UP FOR BREAKING INTERMOLECULAR BONDS RATHER THAN RAISING THE TEMPERATURE - HENSE THE FLAT POINTS ON THE GRAPH.
• SPECIFIC LATENT HEAT - AMOUNT OF ENERGY NEEDED TO CHANGE STATE OF 1KG OF SUBSTANCE WITHOUT CHANGING TEMPERATURE - VARIES FOR DIFFERENT SUBSTANCES AND DIFFERENT STATES CHANGED BETWEEN
• ENERGY = MASS X SPECIFIC LATENT HEAT
• EXPERIMENTS -PLACE SMALL PEICE OF CHOCOLATE ON TOUNGUE - HOLD LUMP OF ICE IN HAND AND ALLOW IT TO MELT

SPECIFIC HEAT CAPACITY

• AMOUNT OF ENERGY NEEDED TO RAISE TEMPERATURE OF 1KG OF A SUBSTANCE BY 1 DEGREE C
• SHC OF WATER HIGH - 4200J - GAINS LOTS OF ENERGY TO WARM UP - RELEASES WHEN COOLS - WATER CAN STORE A LOT OF ENERGY - GOOD FOR HEATING HOUSES
• ENERGY = MASS X SPECIFIC HEAT CAPACITY X TEMPERATURE CHANGE
• ENERGY NEEDED TO CHANGE TEMPERATURE OF SUBSTANCE DEPENDS ON:
• - MASS OF OBJECT
• - SUBSTANCE OBJECT IS MADE FROM
• - AMOUNT OF ENERGY TRANSFERED TO OBJECT

EXPERIMENT TO FIND OUT AMOUNT OF ENERGY NEEDED TO CHANGE TEMPERATURE

• PUT BEAKER OF SPECIFIC MASS OF WATER ON HOT PLATE - MEASURE TEMPERATURE EVERY MINUTE UNTIL IT REACHES A CERTAIN TEMPERATURE - DO CALCULATION

CONDUCTION 

• PROCESS WHERE VIBRATING PARTICLES PASS ON EXTRA KINETIC ENERGY TO NEIGHBORING PARTICLES
• OCCURS MAINLY IN SOLIDS - PARTICLES HELD TIGHTLY TOGETHER - PARTICLE VIBRATES AND BUMPS INTO OTHER PARTICLES - PASSES VIBRATIONS ON
• PARTICLES WHICH VIBRATE FASTER - PASS ON EXTRA KINETIC ENERGY TO NEIGHBORING PARTICLES - NEIGHBORING PARTICLES VIBRATE FASTER - PROCESS CONTINUES AND EXTRA KINETIC ENERGY IS SPREAD THROUGHOUT SOLID - CAUSES RISE IN TEMPERATURE ON OTHER SIDE
• METALS - CONDUCT REALLY WELL - SOME ELECTRONS FREE TO MOVE INSIDE METAL - HEAT MAKES ELECTRONS MOVE FASTER - COLIDE WITH OTHER FREE ELECTRONS, TRANSFERING ENERGY - MUCH FASTER WAY OF TRANSFERING HEAT AS ELECTRONS MOVE FREELY
• NON METALS - NOFREE ELECTRONS - DON'T CONDUCT AS QUICKLY - GOOD FOR INSULATING
• LIQUIDS AND GASES - CONDUCT HEAT MORE SLOWLY - PARTICLES AREN'T AS TIGHTLY PACKED TOGETHER

CONVECTION

• OCCURS WHEN THE MORE ENERGETIC PARTICLES MOVE FROM THE HOTTER TO THE COOLER REGION AND TAKE THEIR HEAT ENERGY WITH THEM
• LIQUID OR GAS HEATED - PARTICLES MOVE FASTER AND FLUID EXPANDS BECOMING LESS DENSE - WARMER, LESS DENSE FLUIDS RISE ABOVE IT'S COOLER, DENSER SURROUNDINGS
• AS WARM FLUID RISES, COOLER FLUID TAKES IT'S PLACE AT THE BOTTOM - PROCESS CONTINUES - END UP WITH CIRCULATION OF FLUID
• RADIATORS IN HOME - RELY ON CONVECTION TO MAKE HOT AIR CIRCULATE AROUND ROOM
• SOLIDS - CONVECTION CAN'T HAPPEN - PARTICLES CAN'T MOVE - JUST VIRATE ON SPOT
• REDUCE CONVECTION - STOP FLUID MOVING - CLOTHES, BLANKETS, CAVITY WALL FOAM WORK AS INSULATION - TRAP POCKETS OF AIR - AIR CAN'T MOVE - HEAT HAS TO CONDUCT ERY SLOWLYTHROUGH POCKETS OF AIR

RADIATION - HEAT RADIATED BY INFARED WAVES - TRAVEL IN STRAIGHT LINES AT SPEED OF LIGHT

• DOESN'T NEED A MEDIUM TO TRAVEL THROUGH - CAN OCCUR IN VACUUM LIKE SPACE - ONLY WAY HEAT REACHES US FROM SUN
• CAN ONLY OCCUR THROUGH TRANSPARENT SUBSTANCES LIKE GLASS, AIR AND WATER

ABSORBING AND EMITING HEAT

• ALL OBJECTS CONTINUOUSLY EMIT AND ABSORB RADIATION - HOTTER OBJECTS EMIT MORE RADIATION
• COOLER OBJECTS - ABSORB HEAT RADIATION EMITTED BY HOTTER THINGS - TEMPERATURE OF COOLER OBJECT INCREASES
• GOOD EMITTERS AND ABSORBERS OF RADIATION - MATT BLACK OBJECTS 
• POOR ABSORBERS AND EMMITERS OF RADIATION - LIGHT COLOURED SMOOTH SHINY OBJECTS - REFLECT RADIATION

EVERYDAY SITUATIONS

• RADIATORS SHOULD BE DARK AND MATT COLOURS
• FRIDGES SHOULD BE LIGHT AND REFLECIVE - FOIL CAN BE PUT ON RADIATORS TO REFLECT HEAT BACK IN

REDUCING HEAT LOSS IN THE HOME USING AIR GAPS

• LOFT INSULATION - FIBERGLASS WOOL LAID ACROSS LOFT FLOOR - REDUCES CONDUCTION THROUGH CEILING INTO ROOF SPACE - AIR SPACES IN WOOL MAKES IT POOR CONDUCTOR - PARTICLES AREN'T CLOSELY PACKED TOGETHER
• CAVITY WALLS AND INSULATION - TWO LAYERS OF BRICK WITH GAP BETWEEN THEM - REDUCES CONDUCTION (AIR POOR CONDUCTOR OF HEAT) - INSULATING FOAM IN GAPS TRAPS POCKETS OF AIR - REDUCES MOVEMENT OF AIR - REDUCES CONVECTION
• DRAUGHT PROOFING - STRIPS OF FOAM AND PLASTIC AROUND DOORS AND WINDOWS - REDUCE CONVECTION - STOP HOT AIR GOING OUT
• DOUBLE GLAZING - TWO LAYERS OF GLASS - AIR GAP BETWEEN THEM - REDUCE CONDUCTION - AIR POOR CONDUCTOR OF HEAT

OTHER WAYS OF REDUCING HEAT LOSS IN HOME

• HOT WATER TANK JACKET - MADE FROM INSULATOR - REUCES CONDUCTION OF HEAT OUT OF TANK
• THICK CURTAINS - REDUCE CONDUCTION AND RADIATION THROUGH WINDOWS - NOT TRANSPARENT - RADIATION CAN'T PASS THROUGH - MATERIAL POOR CONDUCTOR

PAYBACK TIME = INITIAL COST / ANNUAL SAVING

• SINKS - THINGS THAT TRANSFER WASTE OR LOSE ENERGY E.G. WINDOWS
• HOUSES CAN BE INSULATED TO STOP ENERGY LOSS
• INSULATION COSTS MONEY INITIALLY BUT SAVES MONEY LONG TERM - PAYBACK TIME IS HOW LONG IT TAKES TO MAKE THE MONEY YOU INITIALLY SPENT ON INSULATION BACK IN SAVINGS
• DIFFERENT TYPES OF INSULATION HAVE DIFFERENT PAYBACK TIMES
• E.G. IF A HOT WATER TANK JACKET COST £60 AND SAVED YOU £15 A YEAR, IT WOULD TAKE 4 YEARS TO EARN MONEY BACK

THERMOGRAMS 

• OBJECTS WITH DIFFERENT TEMPERATURES GIVE OUT INFARED RAYS OF DIFFERENT WAVELENGTHS - SHOW UP AS DIFFERENT COLOURS ON THERMOGRAM
• IF THERE IS A LOT OF RED ON A PICTURE OF A HOUSE, THE HOUSE IS LEAKING A LOT OF HEAT IN AREAS WHERE DIAGRAM IS RED E.G. IF ROOF IS RED THE OWNER SHOULD GET LOFT INSULATION

EFFICIENCY = (USEFUL ENERGY OUTPUT / TOTAL ENERGY INPUT) X 100

• MACHINES CONVERT ENERGY INTO ANOTHER TYPE OF ENERGY E.G. CARS GET CHEMICAL ENERGY (PETROL) AND CONVERT IT TO KINETIC ENERGY FOR CARS TO MOVE
• TOTAL ENERGY INPUT - ALWAYS SAME AS TOTAL OUTPUT - ONLY SOME OUTPUT USEFUL - ONLY GET A FRACTION OF CHEMICAL ENERGY PUT IN A CAR AS KINETIC ENERGY - REST WILL BE WASTED AS SOUND AND HEAT ENERGY
• NO MACHINE IS 100% EFFICIENT - ALL WASTE ENERGY
• TO WORK OUT EFFICIENCY OF A MACHINE, DIVIDE USEFUL ENERGY OUTPUT BY TOTAL ENERGY INPUT AND MULTIPLY BY ONE HUNDRED TO GET PERCENTAGE E.G. A KETTLE USES 100J OF ENERGY AND USES 70J OF IT AS HEAT AND THE REST AS SOUND - EFFICIENCY IS 70%

SANKEY DIAGRAMS

 THICKNESS OF ARROW REPRESENTS AMOUNT OF ENERGY - LEFT SIDE OF ARROW IS ENERGY INPUT (100% OF ENERGY) - BIGGER ARROW REPRESENTS LARGE AMOUNT OF ENERGY OUTPUT - SMALLER ARROW REPRESENTS SMALL AMOUNT OF ANOTHER TYPE OF ENERGY OUTPUT

THE TRANSVERSE WAVE 

• AMPLITUDE - DISPLACEMENT FROM REST POSITION TO CREST
• WAVELENGTH - LENGTH OF FULL CYCLE OF WAVE - CREST TO CREST - TROPH TO TROPH
• FREQUENCY - NUMBER OF COMPLETE WAVELENGTHS TO PASS A CERTAIN POINT PER SECOND - MEASURED IN HZ WHERE 1 HZ IS ONE WAVE PER SECOND
• WAVE SPEED (M/S) = FREQUENCY (HZ) X WAVELENGTH (M)
• CONVERTING UNITS
• 1KHZ = 1 000 HZ                 1MHZ = 1 000 000 HZ
• IF FREQUENCY GIVEN IN KHZ OR MHZ, CONVERT BEFORE PUTTING IN CALCULATION
• WAVELENGTH SOMETIMES GIVEN IN OTHER UNITS E.G. 30 KM - CONVERT BEFORE CALCULATION
• WAVE SPEED SOMETIMES GIVEN IN STANDARD FORM E.G. SPEED OF LIGHT IS 3 X 10 8 M/S

REFLECTION 

• ALLOWS US TO SEE OBJECTS - LIGHT REFLECTS OFF OBJECTS INTO OUR EYES
• WHEN LIGHT REFLECTS FROM UNEVEN SURFACE LIGHT REFLECTS AT DIFFERENT ANGLES
• WHEN REFLECTED OFF PLANE SURFACE (SMOOTH AND SHINY) IT'S ALL REFLECTED AT SAME ANGLE AND A CLEAR REFLECTION IS FORMED
• ANGLE OF INCIDENCE = ANGLE OF REFLECTION
• TWO ANGLES ALWAYS DEFINED BETWEEN RAY ITSELF AND NORMAL - NORMAL ALWAYS HALF WAY IN BETWEEN TWO RAYS
• (RED LINE IS THE NORMAL) - PERPENDICULAR TP SURFACE AT POINT OF INSIDENCE WHERE LIGHT HITS SURFACE
• PERISCOPES 
• MIRRORS AT 45 DEGREE ANGLE - NORMAL PERPENDICULAR TO MIRROR
• LIGHT GOES SRAIGHT INTO PERISCOPE AND HITS MIRROR AT 45 DEGREES THEN IS RELECTED OFF AT 45 DEGREES FROM NORMAL - HITS OTHER MIRROR AND REFLECTED INTO EYE

DIFFRACTION - WAVES SPREADING OUT WHEN THEY PASS THROUGH A GAP OR PASS AN OBJECT

• AMOUNT OF DIFRACTION DEPENDS ON SIZE OF GAP RELATIVE TO WAVELENGTH OF WAVE - THE MORE SIMILAR THE SIZE OF THE GAP IS TO THE WAVELENGTH OF THE WAVE, THE NARROWER THE GAP IS SAID TO BE AND THE MORE THE LIGHT WILL DIFFRACT
• LIGHT - VERY SMALL WAVELENGTH - CAN ONLY BE DIFFRACTED SIGNIFICANTLY IF GAP IS VERY SMALL
• SOUND - MUCH LARGER WAVELENGTH - CAN HEAR SOMEONE THROUGH OPEN DOOR BUT CAN'T SEE THEM - SOUND WAVE AND DOOR ROUGHLY EQUAL - SOUND DIFFRACTS AND FILLS ROOM - CAN'T SEE THEM UNLESS DIRECTLY OPPISITE DOOR - GAP IS MASSIVE COMPARED TO LIGHT WAVELENGTH - WON'T DIFFRACT ENOUGH
• DIFFRACTION PATTERNS
• IF GAP SAME SIZE AS WAVELENGTH - DIFFRACTION PATTERN OF LIGHT AND DARK FRINGES 
• <-- DIFFRACTION AROUND EDGES OF OBJECT - SHADOW IS WHERE WAVE BLOCKED - WIDER OBSTICLE COMPARED TO WAVELENGTH, LESS DIFFRACTION CAUSED - LONGER SHADOW

REFRACTION - WAVES CHANGING DIRECTION DUE TO CHANGING SPEED WHEN CROSSING A BOUNDRY BETWEEN TWO MEDIUMS

• E.G. LIGHT PASSING FROM AIR TO GLASS
• <-- LIGHT HITS GLASS FACE ON - SLOWS DOWN BUT CARRIES ON IN SAME DIRECTION - SHORTER WAVELENGTH BUT SAME FREQUENCY
• 
• LIGHT HITS GLASS AT ANGLE - PART OF WAVE HITS MEDIUM AND SLOWS DOWN        BEFORE OTHER PART OF WAVE - OTHER PART CARRIES ON AT SAME SPEED BEFORE HITTING MEDIUM AND SLOWING DOWN - BEND 
• LIGHT HITS A DENSER MEDIUM - BENDS TOWARDS NORMAL
• LIGHT HITS LESS DENSE MEDIUM - BENDS AWAY FROM NORMAL
• LIGHT TRAVELLING ALONG NORMAL HITS MEDIUM - NOT REFRACTED

CONTINUOUS SPECTRUM - SPLIT INTO SEVEN DIFFERENT TYPES OF EM WAVES - ALL DIFFERENT WAVELENGTHS - AS WAVELENGTHS ALONG SPECTRUM DECREASE, FREQUENCY INCREASES

ALL FORMS OF EM WAVES TRAVEL IN STRAIGHT LINES AT SAME SPEED THROUGH A VACUUM

DIFFERENT WAVELENGTHS GIVE WAVES DIFFERENT PROPERTIES - SIMILAR WAVELENGTHS HAVE SIMILAR PROPERTIES

REFRACTION OF WHITE LIGHT IN PRISM

• WHITE LIGHT MADE OF OF FULL SPECTRUM OF COLOURS - HITS PRISM - ALL COLOURS HAVE DIFFERENT WAVELENGTHS - ALL REFRACT AT DIFFERENT ANGLES - SEE A SPECTRUM OF COLOURS
• WILLIAM HERSCHEL - DISCOVERED INFARED - TESTED TEMP OF DIFFERENT COLOURED RAYS REFRACTED THROUGH PRISM - TEMPERATURE INCREASE FROM PURPLE TO RED
• USES OF EM WAVES
• RADIO WAVES - CAN TRAVEL THROUGH AIR - USED FOR WIRELESS COMMUNICATION
• MICROWAVES - SHORTER WAVELENGTHS - CAN PASS THROUGH EARTHS ATMOSPHERE - USED FOR SATTELITE COMMUNICATION AND MOBILE PHONES
• INFARED - USED IN REMOTE CONTROLS - EMIT PULSES OF INFARED IN CODES THAT TV LINKS TO SPECIFIC INSTRUCTIONS
• VISIBLE LIGHT - TRAVELS VERY FAST - USED FOR COMMUNICATION IN OPTICAL FIBRES
• WAVE BASED SENSORS - LIMITING EFFECT OF DIFFRACTION
• TELESCOPES AND MICROSCOPES - GAP NEEDS TO BE SMALL AS IT IS USED TO EXAMINE SMALL THINGS - LIGHT WAVELENGTH SMALL - SOME DIFFRACTION - LIMITS RESOLUTION - DIFFRACTION LIMITED

TOTAL INTERNAL REFLECTION

HAPPENS WHEN LIGHT HITS DENSER MEDIUM WITH ANGLE OF INCIDENCE GREATER THAN CRITICAL ANGLE FOR THAT PARTICULAR MATERIAL

ANGLE OF INCIDENCE SMALLER THAN CRITICAL ANGLE - MOST OF LIGHT REFRACTED TO OUTER LAYER - SOME INTERNALLY REFLECTED

ANGLE OF INSIDENCE SAME AS CRITICAL ANGLE - RAY REFRACTED ALONG SURFACE - QUITE A BIT OF ENTERNAL REFLECTION

ANGLE OF INCIDENCE BIGGER THAN CRITICAL ANGLE - NO LIGHT COMES OUT - ALL INTERNALLY REFLECTED

• MORSE CODE -TYPE OF DIGITAL SIGNAL- CODE OF DIFFERENT SEQUENCES OF ON-OFF SIGNALS
• EACH LETTER OF ALPHABET REPRESENTED BY SEQUENCE OF DOTD AND DASHES WHICH ARE PULSES OF LIGHT OR SOUND FOR A CERTAIN AMOUNT OF TIME (DOTS SHORTER TIME, DASHES LONGER TIME)
• E.G. SOS WOULD BE ...---...
• OPTICAL FIBRES - CARRY DATA OVER LONG DISTANCES AS PULSES OF LIGHT 
• WIRE IS A NARROW CORE PROTECTED BY OUTER LAYERS
• RAY OF LIGHT ENTERS FIBRE SO THAT IT HITS BOUNDRY BETWEEN CORE AND OUTER CLADDING AT AN ANGLE GREATER THAN THE CRITICAL ANGLE OF THE MATERIAL - CAUSES RAYS TO BE TOTALLY INTERNALLY REFLECTED OFF SIDES - REFLECTED AGAIN AND AGAIN IN ZIGZAG SHAPE UNTIL EMERGES AT OTHER END OF OPTICAL FIBRE
• INCREASINGLY BEING USED FOR TELEPHONE AND BROADBAND INTERNET CABLES        
• ADVANTAGES TO USING LIGHT
• QUICK - TRAVELS THROUGH VACUUM AT 300 000 000 M/S (SLOWED DOWN BY ABOUT 30% IN OPTICAL FIBRES) 
• MULTIPLEXING - LOTS OF DIFFERENT SIGNALS CAN TRAVEL THROUGH SINGLE OPTICAL FIBRE - ALSO DIGITAL - LITTLE INTERFERENCE

LASERS - PRODUCE NARROW, INSENSE BEAMS OF MONOCHROMIC LIGHT

ORDINARY VISIBLE LIGHT - COMBINATION OF WAVES OF DIFFERENT FREQUENCY AND WAVELENGTH (AND SO COLOUR) THAT ARE 'OUT OF PHASE' WITH EACHOTHER (CRESTS AND TROPHS DON'T MATCH)

LASER - SPECIAL RAY OF VISIBLE LIGHT - PROPERTIES:

- ALL WAVES IN BEAM SAME FREQUENCY AND WAVELENGTH - LIGHT MONOCHROMIC (SINGLE, PURE COLOUR)

- LIGHT WAVES ALL IN PHASE WITH EACHOTHER - TROPHS AND CRESTS LINE UP - INCRESES AMPLITUDE - PRODUCES INTENSE BEAM - SAID TO BE COHERANT (FIXED WAVE DIFFERENCE) - DIFERENCE IS ZERO (ALL WAVES SAME)

- LOW DIVERGENCE - BEAM STAYS NARROW - DOESN'T SPREAD OUT - EVEN LONG DISTANCE FROM LIGHT SOURCE (DOESN'T DIVERGE)

CD PLAYERS

SURFACE OF CD HAS PATTERN OF BILLIONS OF SHALLOW PITS - AREAS BETWEEN PITS CALLED LANDS - LASER SHONE INTO CD REFLECTED FROM SHINY BOTTOM SURFACE AS IT SPINS AROUND IN PLAYER

BEAM REFLECTED FROM LAND TO PIT SLIGHTLY DIFFERENTLY - DIFFERENCE PICKED UP BY LIGHT SENSOR - DIFFERENCES IN REFLECTED SIGNALS THEN CHANGED TO ELECTRICAL SIGNAL

PITS AND LANDS THEMSELF DON'T REPRESENT ON AND OFF - CHANGE IN REFLECTIVE BEAM REPRESENTS ON AND NO CHANGE IN BEAM REPRESENTS OFF

AMPLIFIER AND LOUDSPEAKER CONVERT ELECTRICAL SIGNAL TO SOUND OF RIGHT PITCH AND VOLUME

GRILLS AND TOASTERS

• HEAT FOOD WITH INFARED RADIATION - HEAT RADIATED BY GRILL AND ABSORBED BY SURFACE PARTICLES OF FOOD - INCREASES KINETIC ENERGY - HEAT ENERGY THEN CONDUCTED AND CONVECTED TO CENTRAL PARTS
• LINING GRILL PAN WITH SHINY FOIL - REFLECTS HEAT RADIATION BACK ONTO BOTTOM OF FOOD BEING GRILLED - FOOD COOKED MORE EVENLY 

MICROWAVE OVENS

• USE MICROWAVES TO PENETRATE 1CM INTO OUTER LAYER OF FOOD - THEN ABSORBED BY WATER AND FAT MOLECULES IN FOOD - INCRESES KINETIC ENERGY - ENERGY CONDUCTED OR CONVECTED TO OTHER PARTS
• COVERING FOOD IN MICROWAVE WITH FOIL - DANGEROUS - MICROWAVES REFLECTED AWAY AND WON'T COOK FOOD - CAN CAUSE DANGEROUS SPARKS INSIDE OVEN

WIRELESS COMMUNICATION - MICROWAVES

• MICROWAVED USED FOR COMMUNICATION FROM SATTELITES - E.G. SATELLITE TV AND MOBILE PHONES - WAVELENGTH NEEDS TO PASS EASILY THROUGH EARTHS ATMOSPHERE TO RECEIVER WITHOUT ABSORBTION
• SIGNAL FROM TRANSMITTER IS TRANSMITTED INTO SPACE - PICKED UP BY SATELLITE RECIEVER DISH ORBITING THOUSANDS OF KM ABOVE EARTH - SATELLITE TRANSMITS SIGNAL BACK IN DIFFERENT DIRECTION - RECIEVED BY SATELLITE DISH ON GROUND
• MICROWAVES USED FOR REMOTE SENSING SATELLITES - SE THROUGH CLOUDS - MONITER OIL SPILLS, TRACK MOVEMENT OF ICEBERGS ETC.

MOBILE PHONES - CALLS TRAVEL AS MICROWAVES FROM PHONE TO NEAREST TRANSMITTER

• TRANSMITTERS (MASTS) PASS SIGNALS BETWEEN EACHOTHER AND BACK TO MOBILE PHONE
• POOR SIGNAL IF OBSTICLE BETWEEN TRANSMITTER AND RECEIVER - SHORTER WAVE LENGTH THAN RADIO WAVES - DON'T DIFFRACT AS MUCH - CAN'T BEND ROUND SURFACES
• LOSE PHONE AND SATELLITE SIGNAL IN STORM - MICROWAVE FREQUENCIES USED PARTIALLY ABSORBED BY WATER - SIGNAL LOSS THROUGH ABSORPTION AND SCATTERING

INTERFERENCE WITH MICROWAVES

• SHORTER WAVELENGTH THAN RADIO - DON'T DIFFRACT MUCH - AFFECTED BY CURVATURE OF EARTH - DON'T BEND ROUND IT - BLOCKED BY LARGE HILLS ETC. - CAN'T BEND ROUND THEM
• MICROWAVE TRANSMITTERS NEED TO BE IN LINE OF SIGHT WITH RECIEVER - USUALLY HIGH UP ON HILLTOPS SO THEY CAN SEE EACHOTHER AND POSITIONED FAIRLY CLOSE TOGETHER - HILL OR OBSTICLE BETWEEN PHONE AND RECEIVER = POOR SIGNAL
• MICROWAVE FREQUENCIES USED PARTIALLY ABSORBED BY WATER EVEN THOUGH CAN PASS THROUGH ATMOSPHERE - SOME SIGNAL LOSS DUE TO ABSORPTION, SCATTERING - POOR SIGNAL IN STORM
• INTERFERENCE BETWEEN SIGNALS ALSO AFFECTS SIGNAL STRENGTH

MOBILE MASTS - SOME THINK THEY'RE DANGEROUS - CONFLICTING EVIDENCE

• WAVES USED FOR COMMUNICATIONS NEED TO PASS THROUGH EARTHS ATMOSPHERE - DIFFERENT WAVELENGTH TO MICROWAVES USED IN MICROWAVE OVENS - NEEDS TO BE ABSORBED BY WATER IN FOOD
• ABSORPTION HARMFUL - ABSORBED BY WATER IN LIVING TISSUE - CELLS BURNED OR KILLED
• SOME THINK MICROWAVES FROM PHONES DANGEROUS - NO PROOF - STUDIES CONFLICTING EVIDENCE
• POTENTIAL DANGERS INCLUDE PROLONGED EXPOSURE TO MOBILE PHONE SIGNALS - LIVING NEAR MAST OR CONSTANTLY USING PHONE
• HAVE TO CAREFULLY BALANCE POTENTIAL RISKS AND BENEFITS OF TECHNOLOGY UNTIL KNOW MORE - WHERE WE LOCATE MASTS AND HOW MUCH TIME SPENT ON PHONES

REMOTE CONTROLS - EMIT PULSES OF IR TO CONTROL ELECTRICAL DEVICES

PULSES OF LIGHT ACT AS DIGITAL ON/OFF CODE SIMILAR TO MORSE CODE - DEVICE WILL DETECT AND DECODE PATTERN OF PULSES COMING FROM REMOTE - FOLLOW CODED INSTRUCTION

E.G. TV PROGRAMMED TO ASSOCIATE A CERTAIN SEQUENCE OF ON/OFF SIGNALS FOR 'PLAY THEN REMOTE WILL EMIT THIS CERTAIN SEQUENCE WHEN 'PLAY' BUTTON IS PRESSED

WIRELESS COMUNICATION - PHONES AND COMPUTERS

IR SIGNALS USED IN SAME WAY TO TRANFER INFORMATION BETWEEN MOBILE PHONES AND COMPUTERS OVER SHORT RANGE

MAIN DRAWBACK - ONLY WORKS OVER SHORT DISTANCES - IR BEAM FROM SMALL REMOTE CONTROL IS RELATIVELY WEAK

NEED TO POINT BEAM STRAIGHT AT DETECTOR ON DEVICE - IR WAVES ONLY TRANSMIT IN STRAIGHT LINES

USES OF INFARED AROUND HOME

REMOTE CONTROLS - TRANSFER INFORMATION TO TV AND DVD PLAYERS USING IR

TRANSMITTING INFORMATION BETWEEN MOBILE PHONES AND COMPUTERS - ONLY OVER SHORT DISTANCES

SECURITY SYSTEMS - SENSORS DETECT HEAT FROM INTRUDERS BODY

OPTICAL FIBRES - CAN BE USED INSTEAD OF VISIBLE LIGHT TO CARRY INFORMATION DOWN OPTICAL FIBRES

MONITORING TEMPERATURE

INFARED RADIATION GIVEN OUT BY HOT OBJECTS - HOTTER THE OBJECT, MORE IR IT GIVES OUT 

IR USED TO MONITOR TEMPERATURES - E.G. INFARED SENSORS DETECT HEAT LOSS THROUGH HOUSE

NIGHT VISION EQUIPMENT - DETECTS INFARED RADIATION AND TURNS IT INTO ELECTRICAL SIGNAL - DISPLAYED ON SCREEN AS PICTURE - HOTTER THE OBJECT, BRIGHTER IT APPEARS - USED BY POLICE AND MILITARY

SIGNALS - INFORMATION NEEDS TO BE CONVERTED INTO ELECTRICAL SIGNALS TO BE TRANSMITTED

• SIGNALS SENT OVER LONG DISTANCES DOWN TELPHONE WIRE OR CARRIED ON EM WAVES
• SIGNALS CAN BE ANALOGUE OR DIGITAL

ANALOGUE AND DIGITAL SIGNALS

• ANALOGUE - CAN TAKE ANY VALUE WITHIN CERTAIN RANGE - APLITUDE, FREQUENCY VARY CONTINUOUSLY
• DIGITAL - CAN ONLY TAKE TWO VALUES - ON/OFF OR 1/0 - E.G. DATA ALONG OPTICAL FIBRES USING SHORT PULSES OF LIGHT

ADVANTAGES OF DIGITAL SIGNALS 

• HIGHER QUALITY - SIGNALS WEAKEN AS TRAVEL - NEED TO BE AMPLIFIED - NOISE PICKED UP BY SIGNAL WHEN TRAVELLING FROM ELCTRICAL DISTURBANCES OR OTHER WAVES - WHEN ANALOGUE AMPLIFIED, NOISE ALSO AMPLIFIED - LOSES QUALITY - EASIER TO REMOVE OR IGNORE WITH DIGITAL
• MULTIPLEXING - MANY SIGNALS CAN BE TRANSMITTED AT SAME TIME E.G. PHONES - THOUSANDS OF VOICES TRANSMITTED AND SEPERATED OUT ON OTHER END
• ADVANTAGES PLAYED BIG PART IN SWITCHING OVER FROM ANALOGUE TO DIGITAL TV/RADIO BROADCASTS

THE EARTHS ATMOSPHERE - RADIO AND MICROWAVES USED - LONG WAVELENGTHS - DON'T GET ABSORBED IN EARTHS ATMOSPHERE AS MUCH 

RADIO WAVES - COMMUNICATIONS

• RADIO WAVES - EM RADIATION WITH WAVELENGTH LONGER THAN 10CM
• DIFFERENT WAVELENGTHS OF RADIOWAVE REFRACT AND DIFFRACT IN DIFFERENT WAYS
• LONG WAVE RADIO (1-10KM) CAN BE TRANSMITTED FROM ONE PLACE AND RECIEVED HALFWAY ROUND WORLD - DIFFRACT AROUND CURVED SURFACE OF EARTH
• WAVES USED FOR TV AND RADIO - SHORTER WAVELENGTHS (10CM - 10M) - MUST BE IN DIRECT LINE OF SIGHT OF TRANSMITTER TO GET SIGNAL - DOESN'T BEND AROUND HILLS OR TRAVEL THROUGH BUILDINGS
• SHORT WAVE RADIO SIGNALS (10M - 100M) - CAN BE RECEIVED AT LONG DISTANCE FROM TRANSMITTER DUE TO REFLECTION IN IONOSPHERE
• MEDIUM WAVE SIGNALS - ALSO REFLECT FROM IONOSPHERE DEPENDING ON ATMOSPHERIC CONDITIONS AND TIME OF DAY
• 

DIFFRACTION - WHEN WAVE SPREADS OUT AT EDGES WHEN PASS THROUGH GAP OR PAST OBJECT

• AMOUNT - DEPENDS ON WAVELENGTH OF WAVE RELATIVE TO SIZE OF OBJECT - LONGER WAVELENGTHS ENCOUNTER LOTS OF DIFFRACTION - LARGE COMPARED TO SIZE OF GAP
• LONGER WAVES ABLE TO BEND ROUND CORNERS AND OBSTICLES E.G. HILLS, TALL BUILDINGS
• LONGER WAVELENGTH RADIO WAVES CAN TRAVEL LONG DISTANCES BETWEEN TRANSMITTER AND RECIEVER WITHOUT HAVING TO BE IN DIRECT LINE OF SIGHT OF EACHOTHER 
• AREAS HAVE TROUBLE RECEIVING SHORTER LENGTH RADIO SIGNALS E.G. FOOT OF MOUNTAIN - POOR SIGNAL
• DIFFRACTION CAN OCCUR AT EDGES OF TRANSMITTER DISHES - SIGNAL LOSS/WEAKER - WAVE SPREAD OUT

REFRACTION - WAVE HITS SOMETHING OF DIFFERENT DENSITY AND CHANGES SPEED - CHANGES DIRECTION IF HITS MEDIUM AT ANGLE

• IONOSPHERE - ELECTICALLY CHARGED LAYERS OF IONISED ATOMS IN ATMOSPHERE
• RADIO WAVES TRAVEL FASTER THROUGH IONISED ATMOSPHERE THAN NON IONISED - CAUSES REFRACTION
• SORT AND MEDIUM WAVE - REFRACTED IN IONOSPHERE - REFLECTED BACK TO EARTH - LIKE T.I.R OF LIGHT
• AMOUNT WAVE REFRACTED - DEPENDS ON FREQUENCY AND ANGLE OF ELEVATION - HIGH FREQUENCY/SHORT WAVELENGTH RADIO DON'T REFRACT AS EASILY AS MEDIUM LENGTH

SUMMERY

• MICROWAVES - PASS THROUGH ATMOSPHERE TO SATELLITE RECEIVERS - RECIEVER NEEDS TO BE IN DIRECT LINE OF SIGHT OF TRANSMITTER - PLACED HIGH UP
• SHORT WAVELENGTH RADIO WAVES - REFRACTED IN IONOSPHERE - MORE DIRECT THAN MEDIUM LENGTH (PATH OF REFRACTION MORE POINTY) - RECEIVED WITHOUT DIRECT LINE OF SIGHT
• MEDIUM WAVELENGTH RADIO WAVES - REFRACTED IN IONOSPHERE - LESS DIRECT (MORE CURVED PATH OF REFRACTION)
• LONG WAVELENGTH RADIO WAVES - NOT REFLECTED IN IONOSPHERE - DIFFRACT AROUND EARTH - MORE DIRECT PATH TO RECIEVER - CAN DIFFRACT ROUND OBSTICLES MORE EASILY

EM RECIEVERS - SIZE - DIFFERENT SIZES USED DEPENDING ON SIZE OF WAVE

• DIFFERENT RECIEVERS PICK UP DIFFERENT WAVES E.G. TELESCOPES, MICROSCOPES - MINIMUM SIZE OF RECEIVER DEPENDS ON SIZE OF WAVELENGTH - BIGGER WAVELENGTH = BIGGER RECEIVER
• THIS MINIMISES DIFFRACTION - WAVE SPREADS AND LOSES DETAIL - AMOUNT OF DIFFRACTION DEPENDS ON SIZE OF GAP RELATIVE - GAP SAME SIZE AS WAVELENGTH CAUSE LOTS OF DIFFRACTION
• BIGGER RECIEVER COMPARED TO WAVELENGTH - LESS DIFFRACTION - CLEARER SOUND

DIGITAL AUDIO BROADCASTING - REDUCES INTERFERENCE BY MULTIPLEXING

• LIMITED NUMBER OF RADIO FREQUENCIES THAT CAN BE USED TO TRANSMIT GOOD ANALOGUE SIGNAL - RADIO STATIONS BROADCAST AT SIMILAR FREQUENCIES - CAUSES INTERFERENCE - NOISE
• DAB TRANSMITTED AS DIGITAL SIGNAL - MANY DIFFERENT SIGNALS COMPRESSED AND TRANSMITTED AS SINGLE WAVE - MULTIPLEXING
• TRANSMITTED ACROSS RELATIVELY SMALL FREQUENCY BANDWIDTH - SEPERATED OUT BY RECEIVERS AT OTHER END - NEED DAB RADIO SET TO PICK UP DAB SIGNALS
• LESS INTERFERENCE AND MULTIPLEXING INCREASE NUMBER OF NETWORKS AVAILABLE
• LIMITTED NUMBER OF DAB TRANSMITTERS AT THE MOMENT - SOME AREAS CAN'T RECIEVE DAB AT ALL
• SOUND QUALITY NOT OFTEN AS GOOD AS ANALOGUE - COMPRESSION OF SIGNAL

OPTICAL MICROSCOPES - DIFFRACTION LIMITED

• HAVE TO BE SMALL - USED TO LOOK AT SMALL SAMPLES OF TINY THINGS - WANT TO COLLECT LIGHT FROM VERY SMALL AREA ONLY
• SMALL SIZE - HARD TO GET GOOD RESOLUTION - GAP NEEDS TO BE VERY SMALL - STILL GET SOME DIFFRACTION EVEN THOUGH LIGHT HAS SMALL WAVELENGTH

TELESCOPES - DETECT DIFFERENT TYPES OF EM WAVES TO HELP YOU SEE OBJECTS CLEARER

• DIFFERENT TELESCOPES USED TO COLLECT DIFFERENT EM WAVES - E.G. OPTICAL TELESCOPES RECIEVE VISIBLE LIGHT
• BIGGER TELESCOPES GIVE BETTER RESOLUTION - LESS DIFFRACTION - INFORMATION CLEARER
• TELESCOPES WITH SMALL GAPS - MORE DIFFRACTION - LIMITS RESOLUTION - DIFFRACTION LIMITED
• RADIO WAVES 10M TIMES BIGGER THAN VISIBLE LIGHT WAVES - RADIO TELESCOPES NEED TO BE VERY BIG - STILL DIFFRACTION LIMITED EVEN THOUGH QUITE BIG
• RADIO TELECOPES OFTEN LINKED TOGETHER - SIGNALS COMBINED TO GET MORE DETAILED INFORMATION - ACT LIKE SINGLE GIANT RECEIVER
• BIGGER RECEIVER - CAN COLLECT MORE EM WAVES - MORE INTENSE IMAGE - BIGGER TELESCOPES CAN OBSERVE FUTHER OBJECTS

UV RADIATION AND SKIN CANCER, CATARACTS AND PREMATURE AGING

• UV RADIATION FROM SUN RAYS DAMAGE DNA IN CELLS
• DARKER SKIN - MORE PROTECTION - ABSORBS MORE UV RAYS - KEEPS IT FROM DAMAGING VULNERABLE TISSUE UNDER SKIN - FAIR SKINNED PEOPLE NEED TO WEAR HIGHER SPFS
• SPF 15 - CAN SPEND 15 TIMES AS LONG AS WOULD WITHOUT SPF ON WITHOUT BURNING (AS LONG AS SUNSCREEN REAPPLIED)
• KEPT INFORMED OF RISKS OF UV - RESEARCH MADE PUBLIC THROUGH MEDIA AND GOVERNMENT TELLS PEOPLE HOW TO KEEP SAFE - IMPROVES PUBLIC HEALTH
• SUNBEDS ALSO DANGEROUS - TANNING SALONS HAVE TIME LIMITS

OZONE LAYER - LAYER OF O3 IN ATMOSPHERE THAT ABSORBS UV RAYS FROM SUN - PROTECTS US

• OZONE LAYER DEPLETED FROM CFC'S - CHEMICALS REACT WITH OZONE - BREAK IT UP - DEPLETION ALLOWS MORE UV RAYS TO REACH EARTH

THE HOLE IN THE OZONE LAYER

• ANTARCTICA - WEATHER CAUSES OZONE TO BREAK DOWN IN WINTER OVER IT - USUALLY BUILDS UP AGAIN IN SPRING - BEEN DROPPING RECENTLY
• DEPLETION CLOSELY MONITERED - INVESTIGATE WHY HOLE IS THERE AND HOW TO PREVENT MORE HOLES
• DIFFERENT STUDIES CARRIED OUT ALL OVER WORLD USING DIFFERENT INSTRUMENTS - SCIENTISTS CAN BE CONFIDENT HYPOTHYSIS CORRECT
• LED SCIENTISTS TO CONFIRM CFCS CAUSING DEPLETION OF OZONE - INTERNATIONALLY BANNED

EARTHQUAKES AND SEISMIC WAVES

• EARTHQUAKES PRODUCE SHOCK WAVES - RECORDED USING SEISMOGRAPHS
• TIME TAKEN FOR WAVES TO REACH EACH SEISMOGRAPH MEASURED - PARTS WHICH DON'T RECEIVE SEISMIC WAVES NOTED
• TWO TYPES OF WAVES THAT TRAVEL THROUGH EARTH:
  • P WAVES - LONGITUDAL - TRAVEL FASTER THAN S WAVES - TRAVEL THROUGH SOLIDS AND LIQUIDS
  • S WAVES - TRANSVERSE - SLOWER THAN P WAVES - ONLY TRAVEL THROUGH SOLIDS

SEISMOGRAPH RESULTS

• P WAVES CHANGE DIRECTION ABRUPTLY HALF WAY THROUGH EARTH - SUDDEN CHANGE IN EARTHS PROPERTIES AS GO FROM MANTLE TO CORE
• S WAVES NOT DETECTED IN CORES SHADOW - LIQUID - S WAVES ONLY TRAVEL THROUGH SOLIDS
• P WAVES - SLIGHTLY FASTER THROUGH MIDDLE OF EARTH - SOLID CORE
• S WAVES TRAVEL THROUGH MANLE - SOLID - ONLY MELT IN HOT SPOTS
• WAVE CHANGE SPEED AS PROPERTIES OF MANTLE AND CORE CHANGE - CAUSES WAVES TO GRADUALLY CHANGE DIRECTION - REFRACTION
• CHANGE SPEED GRADUALLY - CURVED PATH
• PROPERTIES CHANGE SUDDENLY - SPEED CHANGES ABRUPTLY - PATH HAS KINK