Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with RA = 0.5RB, and TA = 2TB. Assuming the temperature of space to be negligible, which star radiates the most energy per unit time? a. Star A b. Star B c. Both radiate the same amount of energy per unit time. d. More information is needed in order to make a determination.

Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with RA = 0.5RB, and TA = 2TB. Assuming the temperature of space to be negligible, which star radiates the most energy per unit time? a. Star A b. Star B c. Both radiate the same amount of energy per unit time. d. More information is needed in order to make a determination.

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter28: Quantum Physics

Section: Chapter Questions

Problem 6P

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2. Can we Estimate the Solar Constant? A result from theoretical physics, known as the Stefan-Boltzmann law, states that the total power radiated by a blackbody at temperature T (K) per unit surface area is given by E=GT* where E is radiated power per unit surface area of the blackbody and o is the Stefan-Boltzmann constant equal to 5.67 x 10* Wm?K*. Let's assume that the sun is a perfect blackbody at T= 5783 K and apply the laws of energy conservation to estimate the average incidence of solar energy [W/m] arriving at the top of Earth's atmosphere (we call that incident energy the solar constant). Compare your calculated estimate of the solar constant to that commonly used to model the sun. Assuming the following constants: d = 1.39e9 m=Diameter of the sun de = 1.27e7 m = Diameter of the earth Res = 1.49el1 m = Mean earth-to-sun distance (HINT: use this distance as the radius of a sphere centered on the sun).
QUESTION 2 What is the surface temperature of a star that has a radius of 7.00 x 108 m and emits power at a rate of 5.00 x 1026 watts? Assume that the star is an ideal blackbody and that the temperature of the surrounding region of outer space is 0.000 K. (Hint: o = 5.67 x 10-8 watts/m2K4) %D а. 5430 К b. 5,050 K С. 6,150 К d. 5820 K е. 5,200 K
4. Assuming a filament in a 100 W light bulb acts as a perfect blackbody (e = 1). what is the temperature of the hottest portion of the filament if it has a surface area of 6.3 105 m²? The Stefan-Boltzmann constant is 5.67 x 10-8 J/(s. m². K*). a) 130.8 K b) 1100.21 K c) 2300.21 K d) 5800.5 K 5. During an evening news broadcast in Helsinki, Finland, the meteorologist indicated that the day's lowest temperature was -6.0 °C. The corresponding value of this temperature on the Fahrenheit scale is ........ a) -7.2 °F b) 4.0 °F c) 21.2 °F d) 25.5 °F
1. A sphere of surface area 100 m and temperature 500 K radiates 0.2 MW. Calculate: a. The emissivity of the surface. b. The peak wavelength of radiation emitted. C. The intensity at a distance of 100m from the centre. d. The energy absorbed per second by a 2m disc with albedo 0.6 placed with it's plane perpendicular to the direction of the radiation. e. The temperature of the disc when it reaches equilibrium (emissivity of the disc = 1). P= eAoT A = 0.00289/T G- 5.67 x 10* Wm°K* Page 1 1 1 Q +
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5. Calculate the temperature of the solar surface if the radiant intensity at the sun's surface is 63 MW/m². Stefan-Boltzmann constant o = 5.67 x 10-8 W/m²/K4 6. A 3.0 g bullet moving at 120 m/s on striking a 50 g block of wood is arrested within the block. Calculate the rise of temperature of the bullet if (a) the block is fixed; (b) the block is free to move. The specific heat of lead is 0.031 cal/g °C.
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C 6. For solar collectors, what combination of surface characteristics is required? b. High absorptivity and high reflectivity High absorptivity and high emissivity High emissivity and low absorptivity d. High absorptivity and low emissivity c.
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