One goal of the Russian space program is to illuminate dark northern cities with sunlight reflected to the Earth from a 200-m diameter mirrored surface in orbit. Several smaller prototypes have already been constructed and put into orbit. (a) Assume that sunlight with intensity 1 370 W/m2 falls on the mirror nearly perpendicularly and that the atmosphere of the Earth allows 74.6% of the energy of sunlight to pass though it in clear weather. What is the power received by a city when the space mirror is reflecting light to it? (b) The plan is for the reflected sunlight to cover a circle of diameter 8.00 km. What is the intensity of light (the average magnitude of the Poynting vector) received by the city? (c) This intensity is what percentage of the vertical component of sunlight at St. Petersburg in January, when the sun reaches an angle of 7.00° above the horizon at noon?
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Chapter 33 Solutions
Physics for Scientists and Engineers
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- Assume the mostly infrared radiation from a heat lamp acts like a continuous wave with wavelength 1.50 µm. (a) If the lamp’s 200-W output is focused on a person’s shoulder, over a circular area 25.0 cm in diameter, what is the intensity in W/m2? (b) What is the peak electric field strength? (c) Find the peak magnetic field strength. (d) How long will it take to increase the temperature of the 4.00-kg shoulder by 2.00º C , assuming no other heat transfer and given that its specific heat is 3.47×103 J/kg⋅ºC?arrow_forwardAssume the mostly infrared radiation from a heat lamp acts like a continuous wave with wavelength 1.50 µm . (a) If the lamp’s 200-W output is focused on a person’s shoulder, over a circular area 25.0 cm in diameter, what is the intensity in W/m2 ? (b) What is the peak electric field strength? (c) Find the peak magnetic field strength. (d) How long will it take to increase the temperature of the 4.00-kg shoulder by 2.00º C , assuming no other heat transfer and given that its specific heat is 3.47×103 J/kg ⋅ ºC ?arrow_forwardAt the top of Earth’s atmosphere, the time-averaged Poynting vector associated with sunlight has a magnitude of about 1.49 kW/m2. a. What is the maximum value for the electric field of a wave of this intensity? Give your answer in volts per meter. b. What is the maximum value for the magnetic field of a wave of this intensity? Give your answer in teslas. c. What is the total power radiated by the sun? Assume that the Earth is 1.5×10111.5×1011 m from the Sun and that sunlight is composed of electromagnetic plane waves. Give your answer in watts.arrow_forward
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