Midterm 2011 Solutions

# What part of the electromagnetic spectrum is this

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Unformatted text preview: 9 Physics 160 Fall 2011 Midterm Exam (g) What is the apparent angular size (diameter) of Regulus in arcseconds as viewed from Earth? (h) At what wavelength does the blackbody continuum of Regulus peak in intensity? What part of the electromagnetic spectrum is this? (i) Assuming that it has the same composition as the Sun, why does Regulus have a weaker Hα line? Page 4 of 19 Physics 160 Fall 2011 Midterm Exam (2) The temperature of the Earth. (a) Calculate the solar flux (in W/m2) incident at the top of the Earth’s atmosphere. This is known as the solar constant. (b) What is the total solar power incident on the Earth in W? Be sure to take into account the curvature of the Earth. Page 5 of 19 Physics 160 Fall 2011 Midterm Exam (c) Assume that all solar radiation energy incident on the Earth is absorbed and then re ­radiated in all directions as thermal blackbody emission. Derive an expression for the blackbody temperature of Earth in terms of the Sun’s photospheric temperature, radius and distance from Earth. (d) Evaluate the expression from part (c). Is this temperature greater than or less than the mean temperature on the surface of the Earth (287 K)? Why do you think this is the case? Page 6 of 19 Physics 160 Fall 2011 Midterm Exam (3) The following is the actual spectrum of the star 2MASS J0041 ­5621 in the red optical region, with some particular spectral features noted: Spectral Flux Density H 1.0 Continuum TiO Li I 0.1 655 660 665 670 Wavelength (nm) TiO 675 680 (a) For each of the following features, indicate whether it arose from relatively thin or dense gas and relatively hot or cool gas: Feature Thin or...
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## This document was uploaded on 02/26/2014 for the course PHYS 160 at UCSD.

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