Read the following statements carefully and to the end. For each statement clear
ID: 298329 • Letter: R
Question
Read the following statements carefully and to the end. For each statement clearly discuss: Are there errors in that statement? Provide a full justification for your argument (pro or contra) in 3-5 sentences involving concepts of the lecture!
a. [5p] “It is commonly known that one can supercool water and maintain it as a liquid at temperatures as low as -10°C. If a sample of supercooled liquid water is isolated in a closed, thermally insulated container, after a time it spontaneously changes to a mixture of ice and water at 0°C. Thus, it increases its temperature spontaneously with no addition of heat from outside, and furthermore, some low-entropy ice is produced.”
b. [5p] “Modern technology makes it possible to build “radiation sails”, which collect electromagnetic radiation. Working like giant antennas, the sails convert the radiation into an electric signal, produce a current and deliver work. Such “antenna” work for any wavelength in the spectrum, from radio waves over microwaves to the infra red. Consequently, scientists have recently developed a sail which can harvest the radiation emitted from the water of an ocean (~ 10°C). While, admittedly, still very large sails are required (producing 1 horse power, about 0.75 kW, requires about 100 m2 of sail), the consortium plans to build a prototype to sail around the earth by 2020.”
Explanation / Answer
a.Supercooled water is a phenomenon in which water remains in its liquid form even below its freezing point. The supercooled water at -10 degree celsius has a higher entropy than the ice at the same temperature. This is the reason that the supercooled water if put in a thermally insulated container it does not convert spontaneously into ice.
b. The radiation sail is that in which uses the radiation pressure imposed by sunlight due to reflecting mirrors. As we know that most of the energy provided to the rockets into the space by the fuels. Now the solar energy will be used in the future to propel the ship forward. This could save the fuel. This solar cells basically capture the light energy when they bounce from a reflective surface. We know that every light particle has momentum and when they strike the reflective surface they impart the momentum to them.
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