At midday when a shopping center with a flat black roof is directly under the Sun, it receives 1,025 W of solar power per square meter of surface from the Sun. If this hot surface loses energy only by radiation back into the atmosphere, what is its equilibrium temperature (in K)? u may use an emissivity of e=1 for a black surface

At midday when a shopping center with a flat black roof is directly under the Sun, it receives 1,025 W of solar power per square meter of surface from the Sun. If this hot surface loses energy only by radiation back into the atmosphere, what is its equilibrium temperature (in K)? u may use an emissivity of e=1 for a black surface

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter21: Heat And The First Law Of Thermodynamics

Section: Chapter Questions

Problem 61PQ

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(a) At what temperature do the Fahrenheit and Celsius scales have the same numerical value? (b) At what temperature do me Fahrenheit and Kelvin scales have the same numerical value?
The surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?
At midday when a large construction site covered with black tarps is directly under the Sun, it receives 975 W of solar power per square meter of surface from the Sun. If this hot surface loses energy only by radiation back into the atmosphere, what is its equilibrium temperature (in K)? You may use an emissivity of e = 1 for a black surface.
The intensity of solar radiation reaching Mars averages about 580 W/m2. a) Assuming the Sun radiates as a blackbody, estimate the surface temperature of the Sun. b) Assuming that Mars behaves like a blackbody, how much energy is absorbed per unit time. What is its equilibrium temperature if all this energy is re-radiated back into space?
(1a). Black body has emissivity value of 1, but in reality, the emissivity of real objects is less than 1. Why?e (1b). The tungsten sphere of 240 mm radius is at a temperature of 25°C. If the power radiated by sphere is 91 W, calculate its emissivity value? (1c).If the same sphere is enclosed in room whose walls are kept at -7°C, what is the net flow rate of energy out of the sphere in Watts (W)
A. The planet Venus is different from the earth in several respects: (a) it is only 70 % as far from the sun, so the solar constant is 2800 W/m²; (b) its thick clouds reflect 77% of all incident sunlight and (c) its atmosphere is much more opaque to infrared light. B. (i) Estimate what the average surface temperature of Venus would be if it had no atmosphere and did not reflect any sunlight. (ii) Taking into account the reflectivity of the clouds, estimate the surface temperature. Use the theory of Earth's energy balance to discuss the greenhouse effect.
The next four questions use this description. Our Sun has a peak emission wavelength of about 500 nm and a radius of about 700,000 km. Your dark-adapted eye has a pupil diameter of about 7 mm and can detect light intensity down to about 1.5 x 10-11 W/m². Assume the emissivity of the Sun is equal to 1. First, given these numbers, what is the surface temperature of the Sun in Kelvin to 3 significant digits? 5,796
Solar energy strikes the top of the Earth’s atmosphere at 343 W m−2. About 30 per cent of this energy is reflected directly back into space. The Earth–atmosphere system absorbs the remaining energy and re-radiates it into space as black-body radiation at 5.672 × 10−8(T/K)4 W m−2, where T is the temperature. Assuming that the arrangement has come to equilibrium, what is the average black-body temperature of the Earth? Calculate the wavelength at which the black-body radiation from the Earth is at a maximum.
Betelgeuse, a bright red star in the constellation Orion, has a luminosity that is 100,000 times that of the Sun. However, the surface temperature of Betelgeuse is only 3000 K. Assuming that the emissivity of stars is 1, What is the radius of Betelgeuse?
The next four questions use this description. Our Sun has a peak emission wavelength of about 500 nm and a radius of about 700,000 km. Your dark-adapted eye has a pupil diameter of about 7 mm and can detect light intensity down to about 1.5 x 10-11 W/m2. Assume the emissivity of the Sun is equal to 1. First, given these numbers, what is the surface temperature of the Sun in Kelvin to 3 significant digits? What is the power output of the Sun in moles of watts? (in other words, take the number of watts and divide it by Avogadro's number) Assuming that all of the Sun's power is given off as 500 nm photons*, how many photons are given off by the Sun every second? Report your answer to the nearest power of 10 (e.g. if you got 7 x 1024, give your answer as 25).
Heat flux meters use a very sensitive device known as a thermopile to measure the temperature difference across a thin, heat conducting film made of kapton (k = 0.345 W/m - K). If the thermopile can detect temperature differences of 0.1°C or more and the film thickness is2 mm, what is the minimum heat flux this meter can detect?
We can use Stefan-Boltzmann Law, P = o AeT“, to produce a very rough estimation of temperature of the Earth. Follow the steps below to estimate the temperature of the Earth. At the radius of the Earth's orbit (1 astronomical unit away from the Sun), the thermal radiation from the Sun has an intensity of about S = 1370 W/m², known as the "solar constant." a. In terms of solar constant S and radius of the Earth R, what is the total solar power (Pn) incident on and absorbed by the Earth? Assume that Earth can be treated like a blackbody and will absorb all radiation incident on it. Hint for (a) Pin Give your answer in terms of S, R, and other numerical constants (spell out Greek characters, i.e. "pi" for T). the Earth rises, the power emitted by the Earth (Pout) increases. Give an b. As the temperature expression for power emitted by the Earth, in terms of its radius and other constants (see some of the constants used in Stefan-Boltzmann Law). Hint for (b) Pout Give your answer in terms…