Flashcards
Physics - Waves
Cards in this deck (22)
- 1WAVESWaves transfer energy from one place to another without transferring any matter
- 2AMPLITUDEThe amplitude is the displacement from the rest position to the crest.
- 3WAVELENGTHThe wavelength is the length of a full cycle of the wave. e.g. from crest to crest.
- 4FREQUENCYFrequency is the number of complete waves passing a certain point per second. Frequency is measured in hertz (Hz). 1Hz is 1 wave per second.
- 5TRANSVERSE WAVESIn transverse waves, the vibrations are at 90 degrees to the direction of the travel of the wave.
Most waves are transverse:
1) Light and all the other EM waves.
2) Ripples on water
3) Waves on strings
4) A slinky spring wiggled up and down - 6LONGITUDINAL WAVESIn longitudinal waves, the vibrations are along the same direction as the wave is travelling.
Examples of longitudinal waves:
1) Sound waves (travel faster in denser substances) and Ultrasound.
2) Shock waves
3) A slinky spring when you push the end. - 7ELECTROMAGNETIC SPECTRUM WAVES1) Radio waves
2) Microwaves
3) Infrared
4) Visible light
5) Ultraviolet
6) X - rays
7) Gamma Rays - 8PROPERTIES OF THE ELECTROMAGNETIC WAVES- All forms of electromagnetic radiation travel at the same speed through a vacuum.
- Waves with shorter wavelengths have a higher frequency.
- Also, the ones with high frequency (shorter wavelength), tend to be more dangerous to living cells. That's because they have more energy.
Electromagnetic waves travel more slowly in denser media. - 9DANGERS OF ELECTROMAGNETIC WAVESSome radiations are more harmful than others.
when entering living tissues it is often harmless, but sometimes it can create havoc.
- mostly pass through soft tissues without being absorbed.
- others are absorbed and can cause heating of the cells.
- some can cause cancerous changes in living cells.
Some types of electromagnetic waves can destroy cells. - 10HIGHER FREQUENCY OF ELECTROMAGNETIC RADIATION IS USUALLY MORE DANGEROUSRadio waves have lower frequencies and are less harmful than high-frequency waves like x -rays and gamma rays.
This is because the energy of any electromagnetic wave is directly proportional to its frequency. So higher waves have more energy. And it's the energy of a wave that does the damage. - 11MICROWAVES - MAY OR MAY NOT BE HARMFULSome wavelengths of microwaves are absorbed by water molecules and heat them up.
- 12ULTRAVIOLET CAN CAUSE SKIN CANCERIf you spend a lot of time in the sun, you'll get a tan and maybe a sunburn.
The more time you spend in the sun the more likely you are to get skin cancer. This is because the sun's rays include Ultraviolet radiation. - 13WAVE SPEED, FREQUENCY AND WAVELENGTH FORMULAWave speed = frequency x wavelength
- 14REFLECTIONThe waves might be reflected - so the waves 'rebound off' the material.
When a wave is reflected the angle of incidence is equal to the angle of reflection. - 15REFRACTIONThey could be refracted - which means they go through the new material but change direction.
Waves travel at different speeds in substances which have different densities. - 16DIFFRACTIONOr they could be diffracted - this means the waves 'bend round' obstacles, causing the waves to spread out. This allows waves to 'travel round corners'.
- 17USES OF RADIO WAVESRadio waves and some microwaves are good at transferring information a long way. This is partly because they don't get absorbed by the Earth's atmosphere.
These signals don't diffract much to get reception, you must be in direct sight of the transmitter.
Short-wave radio signals can be received from long distances from the transmitter. This is because they are reflected from the ionosphere - an electrically charged layer in the Earth's upper atmosphere. - 18USES OF MICROWAVESMicrowaves that are used in microwave ovens have a different wavelength from those used in communication.
These microwaves are absorbed by the water molecules in the food. The energy is then conducted or convected to the other parts. - 19USES OF X-RAYSRadiographers in hospitals take x-ray photographs of people to see if they have any broken bones.
X-rays pass easily through flesh but not easy through denser materials.
It's the amount of radiation that's absorbed that gives you an x-ray image.
Can cause cancer => radiographer need to wear aprons and protect themselves. - 20USES OF INFRARED RADIATIONInfrared radiation can be used to monitor temperature.
- Heat radiation - 21ULTRASOUNDUltrasound is made up of high-frequency sound waves.
- 22HUMAN HEARINGThe human hearing is from 20Hz to 20,000Hz.
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- Flashcards on Physics - Waves , created by Paloma Gohil on 10/12/2016.
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