The intensity of solar radiation at the top of Earth’s atmosphereis 1 370 W/m3. Assuming 60% of the incoming solar energyreaches Earth’s surface and assuming you absorb 50% of theincident energy, make an order - of - magnitude estimate of theamount of solar energy you absorb in a 60 - minute sunbath.

The intensity of solar radiation at the top of Earth’s atmosphereis 1 370 W/m3. Assuming 60% of the incoming solar energyreaches Earth’s surface and assuming you absorb 50% of theincident energy, make an order - of - magnitude estimate of theamount of solar energy you absorb in a 60 - minute sunbath.

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter1: Temperature And Heat

Section: Chapter Questions

Problem 122AP: (a) Deter-nine the power of radiation from the Sun by noting that the intensity of the radiation at...

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As the very first rudiment of climatology, estimate the temperature of Earth. Assume it is a perfect sphere and its temperature is uniform. Ignore the greenhouse effect. Thermal radiation from the Sun has an intensity (the "solar constant" S) of about 1370 W/m2 at the radius of Earth's orbit. (a) Assuming the Sun's rays are parallel, what area must S be multiplied by to get the total radiation intercepted by Earth? It will be easiest to answer in tens of Earth's radius, R. (b) Assume that Earth reflects about 30% of the solar energy it intercepts. In other words, Earth has an albedo with a value of A=0.3 . In terms of S, and R, what is the rate at which Earth absorbs energy from the Sun? (c) Find the temperature at which Earth radiates energy at the same rate. Assume that at the infrared wavelengths where it radiates, the emissivity e is 1. Does your result show that the greenhouse effect is important? (d) How does your answer depend on the area of Earth?
When going lrom fat toO muscie tiSSUC, 3. (a) Find energy that the light-skinned person (e = 0.6) with a skin area of A =1.7m2 receives from solar radiation incident at angle 0 = 60°. (b) Find energy that the dark-skinned person (e = 0.8) with a skin area of A =1.7m2 receives from solar radiation incident at angle 0 = 60 %3D %3D %3D
The total rate at which power is used by humans worldwideis approximately 15 TW (terawatts). The solar flux averagedover the sunlit half of Earth is 680 W>m2 (assumingno clouds). The area of Earth’s disc as seen from the Sun is1.28 * 1014 m2. The surface area of Earth is approximately197,000,000 square miles. How much of Earth’s surfacewould we need to cover with solar energy collectors to powerthe planet for use by all humans? Assume that the solar energycollectors can convert only 10% of the available sunlightinto useful power.
Compute the energy consumption in units of joules per year, gigawatts (GW), and watts per person as (a) fuel, (b) food, and (c) solar radiation for a country of population density 20 person/km2, an area of 1 million km2, and a fuel energy consumption rate of 250 GJ per person per year. Solar radiation reaching the ground is approximately 150 W/m2. The average person consumes food containing 2000 “calories” per day (1 calorie = 4182 J).
The rate at which radiant energy from the sun reaches theearth’s upper atmosphere is about 1.50 kW/m2. The distance fromthe earth to the sun is 1.50 * 10^11 m, and the radius of the sun is6.96 * 10^8 m. (a) What is the rate of radiation of energy per unit areafrom the sun’s surface? (b) If the sun radiates as an ideal blackbody,what is the temperature of its surface?
If the energy received by 5 m2 area in 10 minutes is 4200 kJ, calculate the value of solar constant.
(a) Cherry-red embers in a fireplace are at 850ºC and have an exposed area of 0.200m2 and an emissivity of 0.980. The surrounding room has a temperature of 18.0ºC. If 50% of the radiant energy enters the room, what is the net rate of radiant heat transfer in kilowatts? (b) Does your answer support the contention that most of the heat transfer into a room by a fireplace comes from infrared radiation?
A person with skin area 2 m2 and 0.97 radiation efficiency is at rest and has a skin temperature of 28o C in an environment with a uniform temperature of 22o C. Calculate the heat loss rate if the skin temperature is raised by 8o C by vigorous exercise.
Assume, the average radiation intake of the planet earth increases by 120 W/m² momentarily. The planet therefore leaves its thermal equilibrium and starts heating up (neglect additional thermal losses). The total weight of the planet is 6 x 1024 kg. Assume, that we have 1.1 x 109 km³ of sea water and the rest of the planet is rock. The heat capacity of sea water is 3.6 kJ/ kg K, the density is 1 t/m³. The heat capacity of rock is 1.1 kJ/ kg K, the density is 2.9 t/m². Take the cross section area of the planet as A = r² with r being 6500 km. How long does it take, until the temperature of the earth has risen by 3°C? Assume, the full mass of the planet is always on the same temperature. Why is the result much lower than you'd expect? Which of the assumptions is not realistic?
(a) Cherry-red embers in a fireplace are at 850ºC and have an exposed area of 0.200 m2 and an emissivity of 0.980. The surrounding room has a temperature of 18.0ºC . If 50% of the radiant energy enters the room, what is the net rate of radiant heat transfer in kilowatts? (b) Does your answer support the contention that most of the heat transferinto a room by a fireplace comes from infrared radiation?
Calculate the amount of radiation emitted for a unit surface (1 m²) for the following situations. Express your answers in both SI units (in W) and U.S. Customary units (in Btu/h). (a) a hot pavement in Arizona at 52°C (125.6°F) and & ≈ 0.84 rate in W rate in Btu/h W Btu/h (b) a hood of a car at 44°C (111.2°F) and & ≈ 0.91 rate in W W rate in Btu/h Btu/h (c) a sunbather at 38°C (100.4°F) and & ≈ 0.91 rate in W W rate in Btu/h Btu/h
The radiation energy (intensity of the radiation) reaching Earth from the sun at the top of the atmosphere is 1.36×103??2⁄, which is called the solar constant. Assuming that Earth absorb the total power coming from the Sun to the Earth and radiates with the emissivity of 0.8 (not ideal black body) at a uniform temperaturearound the Earth, what would the equilibrium temperature of Earth be?