Flashcards
P2
Cards in this deck (12)
- 1How does light behave?Light is a form of electromagnetic radiation that is emitted in all directions by a range of sources that include the sun, light bulbs and fires. When light meets an object in its path, the light is either absorbed or reflected. If most of the light is reflected then an object will apear light in colour or reflective. If most of the light is absorbed then an object will apear dark. Light that reaches our eyes is absorbed by special cells in our eyes, allowing us to see objects. Recently scientists discovered light can also behave as particles of light. They are massless particles of energy called photons. All electromagnetic radiation can be though of as photons, the higher the frequency the more energy the photons have.
- 2What is the speed of light (in a vacuum)?300,000 km/s
- 3List all the types of electromagnetic radiation from lowest energy to highest energy.Radio waves, microwaves, infrared, visible light (red light has the lowest frequency and violet light has the highest frequency), ultraviolet, X-rays, gamma rays
- 4How do solar cells work?By absorbing electromagnetic radiation, the solar cell's surface absorbs some of the energy carried by sunlight and tranfers it to electrical energy. The amount of energy absorbed by the solar cell depends on the strength/intensity of the radiation arriving at its surface.
- 5What is the intensity of a beam of radition a measure of?It is a measure of the energy transfered each second. Electromagnetic radiation transfers energy in 'packets' of energy called Photons.
- 6Explain the factors that affect the amount of energy arriving per second on a surface from a source of radiation.This depends on the number of photons arriving per second (intensity) and the energy transfered by individual photons. The definition of intensity is the energy transfered per second per square meter. As something gets further from a light source the intensity decreases as the same amount of energy is spread out over a larger area. As the distance doubles, the intensity decreases four-fold.
- 7What has more energy, red or blue light and why is this?Blue light because its photons carry more energy.
- 8What is the equation for light intensity?Intensity = energy transferred per second per metre sqaured
- 9What are ions?Charged particles, caused by an atom gaining or losing an electron.
- 10What is ionisation and how does it happen?This forming of ions. When a high energy photon knocks an electron out of an atom creating a positive ion of the atom and a free electron.
- 11What makes radiation 'ionising radiation' and which electromagnetic radiation is ionising?Having enough energy in the photons to knock an electron out of an atom: high frequency radiation so UV, X-rays, gamma rays.
- 12How is ionising radiation harmful and why is this?If molecules in our cells are ionised then the processes within the cells change. Ultraviolet rays from sunlight can damage skin cells. X-rays can cause cancers to develop and gamma rays can severely damage cells, damaging cells, causing cancers and even cell death. The damage is greater when we are exposed from longer periods of time or to higher intensities of radiation. The ions produced by ionising radiation take part in chemical reactions. Because they are charged particles, these reactions are different from the reactions involving atoms and molecules. In our body cells, processes can go wrong. Damge to DNA in our cells results in mutations and some of these are the starting ponts for cancerous growths.
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- Flashcards on P2, created by alexchownahern on 16/05/2014.
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