The Sizes of Stars. The hot glowing surfaces of stars emit energy in the form of electromagnetic radiation . It is a good approximation to assume e = 1 for these surfaces. Find the radii of the following stars (assumed to be spherical): (a) Rigel, the bright blue star in the constellation Orion, which radiates energy at a rate of 2.7 × 10 32 W and has surface temperature 11,000 K; (b) Procyon B (visible only using a telescope), which radiates energy at a rate of 2.1 × 10 23 W and has surface temperature 10,000 K. (c) Compare your answers to the radius of the earth, the radius of the sun, and the distance between the earth and the sun. (Rigel is an example of a supergiant star, and Procyon B is an example of a white dwarf star.)
The Sizes of Stars. The hot glowing surfaces of stars emit energy in the form of electromagnetic radiation . It is a good approximation to assume e = 1 for these surfaces. Find the radii of the following stars (assumed to be spherical): (a) Rigel, the bright blue star in the constellation Orion, which radiates energy at a rate of 2.7 × 10 32 W and has surface temperature 11,000 K; (b) Procyon B (visible only using a telescope), which radiates energy at a rate of 2.1 × 10 23 W and has surface temperature 10,000 K. (c) Compare your answers to the radius of the earth, the radius of the sun, and the distance between the earth and the sun. (Rigel is an example of a supergiant star, and Procyon B is an example of a white dwarf star.)
The Sizes of Stars. The hot glowing surfaces of stars emit energy in the form of electromagneticradiation. It is a good approximation to assume e = 1 for these surfaces. Find the radii of the following stars (assumed to be spherical): (a) Rigel, the bright blue star in the constellation Orion, which radiates energy at a rate of 2.7 × 1032 W and has surface temperature 11,000 K; (b) Procyon B (visible only using a telescope), which radiates energy at a rate of 2.1 × 1023 W and has surface temperature 10,000 K. (c) Compare your answers to the radius of the earth, the radius of the sun, and the distance between the earth and the sun. (Rigel is an example of a supergiant star, and Procyon B is an example of a white dwarf star.)
Interaction between an electric field and a magnetic field.
The most massive stars in the Universe have a surface temperature that can reach over 50 000 K. Life on planets like Earth cannot exist at 1AU from such stars, it's too hot. Find the emitted power per square meter of peak intensity for a similar star with 43000 K that emits thermal radiation. Express your answer to two significant figures.
The Sun radiates almost like a perfect blackbody at a temperature of T= 5800 K.
a) Show, using the Stefan-Boltzmann law, that the rate at which it radiates energy is - 4x1026 W.
b) If you were at Earth's orbit, in space, how many Sun photons would reach you per second? Assume you have a mass of 70 kg, are spherical and full
of water. You may need to find your cross sectional area and assume all Sun photons move in the same direction.
The Earth reradiates the energy it receives from the Sun as a black body. We can calculate the effective temperature of the Earth using the Stefan-Boltzmann equation F = sT4 where we solve for the Temperature T. We use for the energy flux the amount of energy absorbed per second Le divided by the Earth's surface area from which the energy is radiated 4pd2 so that the flux is = Le/(4pd2). Here d is the radius of the Earth given above and s is the Stefan-Boltzmann constant. And the effective temperature is:Te4 = (Le/(4pd2))/s = Le/(4spd2) = __________________ K4and taking the square root of Te4 twice in succession we get the effective Temperature Te:Te = [Le/(4spd2)]0.25 = _________________ Kfor the temperature of the effective Earth. What is the temperature in the Celsius scale? __________ C. (Do I need to tell you how to convert from Kelvin to Celsius? If you don't know look it up in your textbook!!)
Chapter 17 Solutions
University Physics with Modern Physics, Volume 2 (Chs. 21-37); Mastering Physics with Pearson eText -- ValuePack Access Card (14th Edition)
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