P1 Possible QWCs

The Greenhouse Effect

To some extent, the effect that ‘the greenhouse effect’ puts on the Earth can be positive if the amount of ‘greenhouse gases’ in the atmosphere is not large as it produces a natural heating effect on the Earth. The greenhouse effect only becomes a problem when the accumulation of greenhouse gases becomes abundant in the atmosphere.

The most abundant greenhouse gases in the atmosphere include; carbon dioxide, nitrous oxide, methane and water vapour. When visible light is emitted from the Sun and directed towards Earth, it passes through the atmosphere as it is transparent to the greenhouse gases and the ozone. This visible light is then absorbed by the Earth as longer wavelength infra red radiation. Some of this infra red is then reflected back into space but most of it is ‘trapped’ in the atmosphere by the greenhouse gases, this produces a warming effect on the Earth. The greenhouse gases absorb the infra red radiation and re-emit it at shorter wavelengths producing more heat and thus warming the Earth. Global warming has been associated with the greenhouse effect as it pollutes the air with greenhouse gases which will create a greater greenhouse effect.

Background Radiation

Background radiation is the radiation that naturally occurs and is always around us, it is given out in 3 main ways; natural background radiation, background radiation from space and background radiation from human intervention.

Radiation occurs when unstable radioactive isotopes around us decay and emit one of the 3 types of radiation; alpha, beta and gamma. This process is completely random and nobody can intervene in the decay of these isotopes. A large portion of the background in the UK is given off by rocks, especially granite which gives off radium which is then turned into radon gas. Radon gas is especially high in places like Cornwall where there is a large source of granite. This gas increases the chance of lung cancer and can potentially be dangerous if exposed to large amounts of it daily. Cosmic background radiation is also present from the Big Bang when infra red radiation was given off and eventually stretched and became microwave radiation. Also, radiation from human sources such as nuclear fallout and weapons is present among us today.

Heat

Heat can be transferred in 3 ways; conduction, convection and radiation.

Conduction occurs in solids, the best conductors of heat are metals because of the free electrons present in the metal. The heat is transferred from the hot side of the object to the cooler side in 2 main ways. Firstly, the particles near the heat source warm up and vibrate, passing the heat to the neighbouring particles until the heat has reached the cooler side. Secondly, the sea of free electrons helps to carry the heat from the heat source to the cooler region of the object. Convection occurs in gases and liquids as the particles are free to move. The hot air or liquid nearest to the heat source rises as it becomes less dense and heats the cooler particles. After sharing the heat with the cooler particles, the particles become denser and fall to the bottom and get reheated. This cycle continues and is known as convection current. Radiation occurs in solids. Dull and black objects are good absorbers and emitters of heat whereas shiny and silvery objects are poor absorbers and emitters of heat but are good reflectors of heat.

Red Shift

Cosmological red shift was discovered due to Hubble’s theories and measurements. Red shift refers to the shifting of light to the red end of the spectrum as the object moves further away from us. This is explained by the fact that the wavelength of the object increases and frequency decreases as it stretches to move away from us. The faster an object is moving away from us, the greater the red shift due to the greater ‘stretching’ it experiences. Compare a galaxy close to Earth and a galaxy 10AU away from us, the red shift would be greater in the galaxy further away as it has travelled further and the wavelength is greater. Red shift supports the Doppler Effect which proposes the same concept, but with the medium of sounds rather than light. Cosmological red shift is not due to the expansion of an individual body but the expansion of space itself due to the Big Bang Theory when all matter exploded in a singularity in the Universe millions of years ago.