P1 - Waves Flashcards
List the EM wavesfrom longest to shortestwave length.
radio, micro, IR, visible, UV,X-Ray, gamma
State one differencebetween UV and visible light.
UV has a higher frequency,shorter wavelength, has moreenergy
What does redshift tellscientists about galaxies?
that they are moving awayfrom Earth
Why is the redshift notthe same for all galaxies?
galaxies are moving awayfrom Earth at differentspeeds
What does redshiftsuggest about the Universe?
that it is expanding
What happens when ametal aerial absorbs radiowaves?
it creates an alternatingcurrent with the samefrequency as the radio wave
Why would an X-raytelescope placed on Earth notbe able to detect X-raysemitted from distance stars?
X-rays cannot penetrate theatmosphere
Give an example of IRbeing used forcommunication.
TV, remote controls, opticalfibres, remote control,thermal imaging
Give the differencebetween transverse andlongitudinal waves.
oscillations areperpendicular to the directionof energy transferred fortransverse waves but parallelfor longitudinal waves
Why can you hear butnot see the TV in anotherroom?
light waves will notdiffract but sound waves willbecause the width of thedoor is similar to thewavelength of the soundwave.
Why do thermalimaging cameras work betterat night than during the day?
at night the surroundingsare cooler so they emit lessIR than a person; thedifference in IR emitted islarger
Give two properties ofall EM waves.
Travel at the same speed,transfer energy, travel througha vacuum, can be reflected,refracted, diffracted, absorbed,are transverse, travel in straightlines
What is the propertyof microwaves that allowsthem to be used for satellitecommunications?
They can pass through theionosphere.
An image in the mirroris virtual. Why?
Image is formed byimaginary rays crossing;formed behind the mirror
if microwaves areabsorbed by a tennis ball,what effect do themicrowaves have on the ball?
Make it hotter
How does red shiftprovide evidence for the BigBang theory?
Redshift of distant galaxies isgreater which means that thefurther apart galaxies are thefaster they are moving awayfrom each other; relationship isproportional, so must havestarted at same point.
Compare a quiet andlow pitch sound to a loud andhigh pitch sound.
Low pitch has longerwavelength and lowerfrequency/ Quieter sound haslower amplitude
What is cosmicbackground radiation?
Microwave noise thatreaches Earth from manystars and galaxies; radiationcreated just after the BigBang
How do you calculatewave speed?
wave speed (m/s) =frequency (Hz) x wavelength(m)
Describe the Big Bangtheory.
Universe started in oneplace; huge explosion tookplace and sent matteroutwards; Universe has beenexpanding ever since.
What is the Universe?
innumerable collectionof galaxies
What is redshift?
light moves towards thered end of the spectrum
Describe how thesound changes when a cardrives past you.
car drives towards you:wavelength shortens andfrequency increasesCar drives away from you:wavelength lengthens andfrequency decreases
Why do scientists useX-ray, gamma ray andmicrowave telescopes toobserve the Universe?
stars emit different typesof EM radiation
How is the wavelengthof CMBR likely to changeover the next billion years?
increase as Universecontinues to expand
What is the Dopplereffect?
change in wavelength andfrequency when the source ofwaves or observer moves( relative to each other)
Give one example ofmicrowaves being used forcommunications.
Mobile phone/satellitecommunications
What are the dangersof IR, UV and micro waveradiation?
IR- skin burnsUV- skin burns, skin cancerMicrowaves- burns, cancer
Give a use of radiowaves.
TV broadcasting, mobilephone communications
Describe an imageformed in the mirror.
virtual and upright, samedistance behind the mirror asobject is in front of themirror
What is refraction?
when light travels fromone medium to another, itchanges direction because it’sspeed has changed; this isdue to the density of themedium having changed
What are sound wavescaused by?
vibrations
How can you reducethe amount of noisetransmitted through walls?Why does the method work?
panel the walls with woodor plaster or similar so thesound is reflected back orabsorbed
What is diffraction?
the spreading of waves whenthey pass through a gap oraround the edges of an obstaclewhich has a similar size as thewavelength of the wave
How do microwavesheat food?
microwaves are absorbedby the water inside the food,the water heats the food
What does the termfrequency mean?
number of waves persecond
What do the wordscompression and rarefactionmean?
compression is squeezingtogether, rarefaction isstretching apart
What is the law ofreflection?
angle of incidence = angleof reflection
What are the twomain pieces of evidence forthe Big Bang theory?
Redshift and cosmicmicrowave backgroundradiation
