AstroHw2

# AstroHw2 - 2 a Suppose that you traveled to planet whose...

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2. a) Suppose that you traveled to planet whose mass is the same as Earth’s, but whose radius is twice that of the Earth’s. Would you weigh more or less on that planet than on Earth? By what factor? b) Suppose instead that the planet has a radius equal to that of Earth, but it has three times the mass of Earth. Would you weigh more or less on this planet than on Earth? By what factor? c) How are the escape speeds from the planet surfaces in a and b related to the escape speed from the Earth’s surface? A) If the planet has a lower density than one would weigh less than on earth. Moon would be a perfect example. 2 times lighter than it would have been on earth. B) The person would weigh more than they would on earth because the density of the planet is a lot higher. One would weigh 3 times more. C) Escape speed is determined by the gravitational pull of the planet. If the planet is denser than Earth it would have a greater gravity and thus the escape speed would be much smaller. 3. What is the frequency of yellow light of wavelength 500 nm? What is the wavelength of radio waves whose frequency is 91.5 MHz (the transmission frequency of KUSC)? Yellow light 10^-9X500nm=0.0000005m (3X10^8m/s)/(.0000005)= 6X10^14 Hz Radio wave frequency (3X10^8m/s)/91.5 MHz=3.28X10^6nm 4. a) If light consists of particles, then how might one represent the intensity of light (of a particular given color)? If light is a wave, then how might one represent the intensity of light (of a particular given color)? Remember: Intensity is the energy transferred per unit area per unit time. b) Give an example of some physical behavior that distinguishes a wave model of light from a particle model of light. a) In order to represent the intensity of the light one can measure the kinetic energy of it that comes in the form of heat. As for the wave factor, one can perform the experiment performed by Thomas Yong, sending the light through a piece with small slits in it. The dark and the light bands would be representative of the intensity. b) One can measure the heat received by the light due to its frequency, thus showing that light is a particle mode. The waves can be seen in rainbows as the refraction of each wavelength separates the colors. 6. Suppose that a star has a dominant wavelength of emission of 100 nm. Is this star visible to the Human eye? If so, how will appear in terms of color? The star emits light most intensely in the ultraviolet and thus it is not visible to the human eye as it does not follow between 400nm and 700nm. However, in the visible part of the spectrum the star would have been a purple/buish color. 7. What is a “wave packet” model of light? What (if any) advantages does it have over the simple wave model? According to the simple wave model of light, the speed of the electrons should be related to the intensity

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## This note was uploaded on 03/24/2008 for the course ASTR 100Lxg taught by Professor Dappen during the Fall '07 term at USC.

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AstroHw2 - 2 a Suppose that you traveled to planet whose...

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