Fichas
Physics revision
Fichas del conjunto (16)
- 1Analogue and digital similarities and differencesA: denoted by sine waves
D: denoted by square waves
A: From human voice in air
D: From computers, CDs and DVDs. - 2Explain about P wavesP waves are longitudinal.
They travel through both solids and liquids.
They travel faster than S waves. - 3Explain about S wavesS waves are transverse and only travel through solids.
- 4What are shockwaves?Shockwaves from earthquakes can be detected by seismometers and recorded on a seismometer. Shockwaves from earthquakes can cause damage to buildings and affect the earth's surface and tsunamis.
- 5Explain about shock wavesThe speed of P waves and S waves increases as they travel deeper into the mantle. They travel through the earth in curved paths but they change direction suddenly as they pass the boundaries of substances in different states (layer of outer core to inner).
- 6What can happen to seismic waves?They can be reflected and refracted at boundaries between the crust, mantle and core. This means they change direction. They reflect and refract also as they go into different rock types.
- 7What is Specific Heat capacity?Specific Heat Capacity is a property of material that helps you work out how much energy it will take to raise its temperature. In degrees celcius, it's the energy needed to raise the temperature of a 1g block of material by 1 degree.
- 8What will a high specific heat capacity mean?The material takes alot of energy to heat up, and has to lose alot of energy to cool down.
- 9Where does heat flow and how does an object could down depending on its surroundings?Heat always flows from hotter to cooler bodies. The hotter something is in comparison to its surroundings, the quicker it will cool down.
- 10What are the KNOWN issues for mobile phones?• There are limits to the amount of microwave radiation emitted from phones. Specific Absorption rate should not be more than 2 watts per kilogram.
• Radiowaves emitted by the mobile phone specifically endangers the eyes and other areas of the body, due to little blood flow in those specific organs. This means that carrying away excess heat is less effective and can cause problems. - 11What are the SUSPECTED issues?• ELECTRICAL INTERFERENCE - Possibility that microwaves from mobile phones can interfere with hospitals and electrical equipment on aeroplanes.
• SERIOUS HEALTH ISSUES - Microwaves can cause DNA alterations in cells, leading to cancer or infertility. This depends on the SAR. The higher the SAR, the more energy your body is absorbing. Different phones have different SARs.
• BRAIN DAMAGE - Having the mobile phone near the brain is suspected to cause subtle effects. World Health Organisation concluded that microwaves lead to an increased risk of Glioma - a malignant type of brain cancer. A close watch should be kept on this.
• RISKS TO CHILDRN - Children's nervous system isn't yet developed, and children have thinner skulls. - 12What are the ways to reduce signal loss of microwaves?Repeater stations
Higher masts
Line of sight signal - 13Explain briefly about mobile phone usage.Mobile phones use microwave signals. Mobile phones communicate with their base stations using low-intensity microwave radiation. Microwaves can be used to transmit information over large distances, although some areas have poor signals. The use of mobile phones means people are exposed to microwave radiation in two ways:
to the head from the aerial in the phone
to the body from transmitters in base station masts.
The evidence of dangers of mobile phone usage is not conclusive, therefore it is not easy to decide on the siting of mobile phone masts. - 14What does the EM spectrum consist of, and give examples?Gamma ray - surgical instrument
X ray - see bones
Ultra-violet - sun beds, CCTV
Light - fibre optics
Infrared - remote controls
Microwaves - Mobile phones
Radiowaves - Visible light used for communication
(As the wavelngth decreases, the energy and frequency increases) - 15What half of the EM spectrum is harmful and what half is safe?Radiowaves ---> light waves: UNHARMFUL
UV light ---> Gamma: HARMFUL - 16What does amplitude, wavelength, frequencey, trough and crest mean?Amplitude - maximum displacement
Wavelength - distance between successive crests or troughs.
Frequency - Number of waves per second that pass a particular point
Crest - highest point on a wave
Trough - lowest point on a wave
Información
- Descripción
- Fichas sobre Physics revision, creado por N H el 19/01/2015.
- Creado por
- N H
- Visitas
- 0
- Valoración