Flashcards
Waves Pt2
Flashcards do conjunto (20)
- 1Sound Waves-Longitudinal Wave
-Their vibrations occur in the same direction as the direction of travel
-Can only travel through a solid, liquid, gas - 2VibrationsWhen an object or substance vibrates, it produces sound:
-the greater the amplitude, the louder the sound
-the greater the frequency, the higher the pitch - 3Echoes...are reflections of sounds.
- 4The Range of Human HearingThis is between about 20 Hz and 20 kHz, but the range becomes less as we get older. Sounds with frequencies above about 20 kHz are called ultrasound.
- 5Amplitude, Frequency, Loudness and PitchSame frequency = Same pitch
Greater amplitude = Louder
Same amplitude = Same Loudness
Greater frequency = Higher pitched - 6The Electromagnetic SpectrumThe electromagnetic spectrum is a continuous range of wavelengths. The types of radiation that occur in different parts of the spectrum have different uses and dangers, which depend on their wavelength and frequency.
- 7Refraction from a prism-White light can be split up using a prism -The light waves are refracted as they enter and leave the prism. The shorter the wavelength of the light, the more it is refracted. As a result, red light is refracted the least and violet light is refracted the most, causing the coloured light to spread out to form a spectrum
- 8Electromagnetic Spectrum Lowest - Highest (Radio - Gamma)Radio Waves (t.v signals)
Microwaves (cooking, mobile phones)
Infrared (optical fibre communication)
Visible Light (seeing)
Ultra-Violet (detecting forged bank notes)
X-rays (medical images of bones)
Gamma Radiation (killing cancer cells) - 9Wavelengths in the Electromagnetic SpectrumRadio waves have the lowest frequencies and longest wavelengths, while gamma waves have highest frequencies and shortest wavelengths.
The wavelengths vary across the electromagnetic spectrum from about 10–15 m to more than 104 m. - 10Radio WavesRadio waves are used to transmit television and radio programmes. Television uses higher frequencies than radio.
- 11A radio programme receiver...does not need to be directly in view of the transmitter to receive programme signals. Diffraction allows low-frequency radio waves to be received behind hills, although repeater stations are often used to improve the quality of the signals.
- 12The lowest frequency radio waves are...also reflected from an electrically charged layer of the upper atmosphere, called the ionosphere. This means that they can still reach receivers that are not in the line of sight because of the curvature of the Earth's surface.
- 13MicrowavesMicrowave radiation can also be used to transmit signals such as mobile phone calls. Microwave transmitters and receivers on buildings and masts communicate with the mobile phones in their range.
- 14Some people think that mobile phones...which transmit and receive microwaves, may be a health risk. This is not accepted by everyone, as the intensity of the microwaves is too low to damage tissues by heating, and microwaves are not ionising.
- 15Certain microwave radiation wavelengths...pass through the Earth's atmosphere and can be used to transmit information to and from satellites in orbit. Satellite television signals use microwaves.
- 16Communicating with waves: visible light and infraredRadio waves, microwaves, visible light and infrared can all be used for communication.
- 17Visible lightVisible light is the light we can see. It allows us to communicate with one another through books, hand signals and video, for example.
- 18Visible Light 2The use of visible light needs the transmitter and receiver to be in the line of sight. But it is more secure against eavesdroppers than radio waves. Cameras let us record still pictures and movies, and photography is an important use of visible light. Very bright light can damage our eyes – you should never look directly into the Sun.
- 19InfraredWe cannot see infrared radiation, but we can feel it as heat energy. High intensity infrared is used in heaters, toasters and grills, and it can cause burns. Infrared sensors can detect heat from the body. They are used in:
security lights
burglar alarms. - 20Infrared 2Infrared radiation is also used to transmit information from place to place, including:
remote controls for television sets and DVD players
data links between computers.
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- FlashCards sobre Waves Pt2, criado por Kiera Ashford em 17-04-2017.
- Criado por
- Kiera Ashford
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