P1 Revision 8
- Created by: LBC0502
- Created on: 14-06-14 14:20
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- P1 Revision
- Sound and the Doppler Effect
- Speed cameras emit radiowaves which reflect off a car. If the car is moving towards the camera, the reflected waves are more bunched up which decreases their wavelength, the faster the car is moving.
- As well was being loud or soft, this is the amplitude. Sounds can be high or low. This is called the pitch, this is the frequency. Humans have a fairly limited range of pitch they hear (20Hz to 20,000Hz). Many animals can hear sounds which are too high or low for us to hear. Infra-sound travels with a long wave and a low frequency. Ultra-sound is beyond the human range of hearing.
- Low pitch, small amplitude (long wavelength, small height). Higher pitch, small amplitude (short wavelength, small height). Low pitch, large amplitude (long wavelength, large height). Higher pitch, larger amplitude (short wavelength, large height)
- High pitch sounds have higher frequency and a shorter wavelength. Low pitch sounds have a lower frequency and a longer wavelength.Sound travels faster in the air than in steel because these materials have different densities.
- The Doppler Effect: a) The source (e.g. ambulance) is moving towards the observer (e.g. the person). The waves become bunched together. The wavelength decreases. The frequency increases. The sound has a higher pitch. b) The source (e.g. ambulance) is moving away from the observer (e.g. the person). The waves spread out. The wavelength increases. The frequency decreases. The sound has a lower pitch.
- In space, there is a vacuum with no particles. There is no sound in space because sound needs particles to travel and sound travels in longitudinal waves.
- Electromagnetic Spectrum
- Infrared: detectors can be used to track and observe warm objects e.g. rockets, people, nocturnal animals, also used for heaters, grills, remote controls, cable internet. Dangers: Too much infrared radiation could case overheating.
- Microwaves: used in cooking/microwave ovens, water molecules absorb the microwaves to become hot/cooked, satellite transmissions and mobile phones. Dangers: can cause small heating effect on the brain, could cause cataracts which is a clouding of the lens.
- Ultraviolet: sterilisation of materials, UV lamps and sunbeds, marking goods with UV pens in crime prevention/detection.
- Radio waves: used to carry signals for radar, telephones, radio, television and communication (WiFi). Dangers: large doses of radio waves cause cancer/other disorders. Overhead power cables with low frequency fields near homes can affect health.
- Visible light: electric light bulbs, photography, some cable internet connection. Dangers: Too much light can damage the retina in your eye.
- All waves in the electromagnetic spectrum travel at the same speed: 3x105m/s (speed of light). Radio waves, Microwaves, Infrared, Visible light, Ultraviolet, X-rays, Gamma. (Red Martians Invade Venus Using X-ray Guns).
- Gamma: used for treatment for cancer tumours and sterilisation of medical instruments and food. Dangers: kills humans cells with shorter wavelengths and transfers lots of energy. Can cause cancer with mutations in DNA of cells.
- Gamma ray (wavelength=10-12, frequency=1020), X-ray (wavelength=10-10, frequency=1018), Ultra violet (wavelength=10-8, frequency=1016), Visible light (purple to red) (wavelength=0.5x106, frequency=1015), Infrared (wavelength=10-5, frequency=1012), Microwaves (wavelength=10-2, frequency=108), Radio waves (wavelength=103, frequency=104).
- X-rays: used to examine broken bones/teeth, detect diseases in areas of the body and finds defects in metal products. Dangers: can kills human cells by transferring lots of energy and could cause birth defects.
- Communication and Optics
- Communicate: talking, mobile phone, internet, post. Communicating Digital TV - Remote reporting: Progamming source to satellite to DBS Provider Broadcast Centre to satellite to the satellite dish and the receiver (TV)
- Are mobile phones safe? For: microwaves are safe. Flat panel TVs, computers shine a light through liquid crystal display and don't give off any microwaves/radio waves. Experts say there is no proof that health problems were caused by radiation.
- Against: Evidence is not clear about whether radiation is dangeroius. Exposed to high levels of em radiation results to headaches and panic attacks. High levels of radiation have caused brain tumours. Early experiments show high levels of radiation heat up human tissue. Recent studies show temperature inside a person's head changes when using a mobile phone. People living near power cables could get diseases such as cancer (damage to DNA in cells), Alzheimer's disease and breathing problems.
- The IV and DV can be linked: IV affects the DV, the DV supports the IV and the two variables either support or doesn't support the prediction.
- Red **** and the Big Bang
- Red light has the longest wavelength and has the lowest frequency. Red Shift was first noticed by Edwin Hubble. Red Shift/Doppler Effect happens with light.
- Why does light from distant galaxies appear red? (5 marks).- The doppler effect. The galaxy is moving away from the Hubble telescope. The waves spread out and the wavelength increases. The frequency decreases and light is shifted to the red end of the spectrum and the light appears red.
- Why does light from close galaxies appear blue? (5 marks)- The doppler effect. The galaxy is moving towards the Hubble telescope. The waves are bunched together and the wavelength decreases. The frequency increases and light shifted to the blue end of the spectrum and the light appears blue.
- Big Bang Theory: Theory of how the universe was created. No matter/nothing. Explosion from a point. Creating energy. Rapid expansion. Energy created matter. Production of cosmic background radiation detected in all directions. Hydrogen/Helium formed, creating stars.
- Expanding Universe: galaxies moving away, red shift, doppler effect.
- Sound and the Doppler Effect
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