Flashcards
Higher Radiation and Matter definitions
Cards in this deck (31)
- 1Constructive interferencewhen two waves meet in phase, so amplitudes add
- 2Destructive interferencewhen two waves meet out of phase, so they cancel eachother out
- 3wavelength of RED LIGHT(roughly)
650nm - 4wavelength of GREEN LIGHT(roughly)
540nm - 5wavelength of BLUE LIGHT(roughly)
480nm - 6comparing spectra from prisms and gratingsPRISM
~ one spectrum
~ bright
~ red deviated least, violet most
GRATING
~many spectra
~ less intense
~ red deviated most, violet least - 7Photoelectric effectwhen metals are exposed to high-frequency electromagnetic radiation ( eg UV ), electrons are ejected from their surface
- 8Threshold frequencythe minimum frequency of electromagnetic radiation required in order to eject electrons from a particular metal
- 9Point SourceIf a point source irradiates light uniformly in all directions and there is no absorption, then irradiance decreases in proportion to the square of the distance from the object
- 10what does LASER stand for?Light
Ampliication by
Stimulated
Emission of
Radiation - 11Emission of light (photons)light is emitted with electrons in an excited state drop to a lower energy level
- 12Absorption of light (photons)the photon energy s absorbed and the electron will jump to a higher energy level (if the photon's energy is an exact match for the difference in energy between levels)
- 13Laserswork by stimulating the emission of identical photons
light is monochromatic, coherent, parallel and has very high irradiance
note: LASER IS NOT A POINT SOURCE - 14n-type semiconductor~ majority of free charge carriers are negative (electrons)
~ electrically neutral
(~usually silicon doped with arsenic) - 15p-type semiconductor~ majority of free charge carriers are positive (holes)
~ electrically neutral
(~ usually silicon doped with indium) - 16p-n junctionp-type and n-type semiconductors next to each other. some electrons drift from n-type to fill holes in p-type.
This forms a DEPLETION LAYER - depleted of charge carriers so is an insulator - 17p-n junction in forward biasA very small voltage is needed to overcome depletion layer ( 0.7V )
Electrons flow into depletion layer then through holes in p-type
Depletion layer is reduced
Diode conducts electricity - 18p-n junction in reverse biaselectrons in n-type are pulled away +ve
holes in p-type are pulled away by -ve
depletion layer widens
Diode does not conduct (until 'breakdown voltage' is reached) - 19L.E.D.when LED conducts, electrons combine with holes to give out energy as photons of light
- 20PhotodiodeWhen a photon of light enters the depletion layer, its energy can be absorbed and an electron-hole pair created
- 21Photodiode in photovoltaic modethere is a zero bias voltage
photodiode acts as a solar cell
Electron-hole pairs create voltage or e.m.f. - 22Photodiode in photoconductive modephotodiode is connected in reverse bias
photons shining on the depletion layer create electron-hole pairs
The free charge carriers lower the resistance and allow a small current
Acts as an LDR - 23what does MOSFET stand for?Metal
Oxide
Semiconductor
Field
Effect
Transistor - 24How does a MOSFET work?an electric field is set up between gate and substrate electrons, which draws up electrons
A narrow channel of negative charge carriers is created between source and drain, allowing charge to flow - 25Findings of alpha paticle - gold experiment~ most particles passed straight through
~ some were deflected through large angles
~ very very few bounced back - 26conclusions of alpha particle - gold experiment~ most of the atom must be empty space
~ most of the mass and positive charge are concentrated in a very small area
~ the mass is very large compared to an alpha particle - 27Spontaneous Fissiona large, unstable nucleus splitting into two daughter products and releasing energy
- 28Induced Fissionlarge nucleus absorbs a neutron, becoming unstable and splits into two daughter products, releasing energy
- 29Nuclear fusionThe joining of two nuclei to form a nucleus of larger mass number, releasing energy
- 30why is energy released in fission and fusion?mass of reactants is greater than mass of products /
there is a mass defect - 31Average annual effective dose of radiation2 mSv
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- Higher Physics (Unit 3 - Radiation and Matter) Flashcards on Higher Radiation and Matter definitions, created by kerryrandfield on 29/04/2015.
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