Homework I
PHY207: Thermal and Statistical Physics
1. A thermometer is laid out in direct sunlight. Does it measure the temperature of the air, or of the sun, or of some thing else? Explain.
2. What is the temperature of vaccum? Explain.
3. A newspaper article about the weather states that “the temperature of a body measures how much heat the body contains.” Is this description correct? Why or why not?
4. Suppose you come across old scientific notes that describe a temperature scale called °Z on which the boiling point of water is 65.0 Z and the freezing point is -14.0 °Z. (a) What temperature change T on the Z scale would correspond to a change of 53.0 F°? (b) To what temperature on the Fharenheit scale would a temperature T = -98.0 °Z correspond?
5. To measure temperatures, physicists and astronomers often measure how the intensity of electromagnetic radiation emitted by an object varies with wavelength. The wavelength lmax at which the intensity is greatest is related to T, the temperature of the object in kelvins, by lmax T = 0.2898 cm.K. In 1965, microwave radiation peaking at lmax = 0.107 cm was discovered coming in all directions from space. To what temperature does this correspond? The interpretation of this background radiation is that it is left over from some 15 billion years ago, soon after the universe began.