Assume the mostly infrared radiation from a heat lamp acts like a continuous wave with wavelength 1.50 µm . If the lamp’s 200-W output is focused on a person’s shoulder, over a circular area 25.0 cm in diameter, then how long will it take to increase the temperature of the 4.00-kg shoulder by 2.00°C, assuming no other heat transfer and given that its specific heat is 3.47 × 103 J/kg. °C ?

The emissivity of the human skin is 97.0 percent. Use 35.0 °C for the skin temperature and approximate the human body by a rectangular block with a height of 1.61 m, a width of 37.5 cm and a length of 22.0 cm. Calculate the power emitted by the human body. What is the wavelength of the peak in the spectral distribution for this temperature? Fortunately our environment radiates too. The human body absorbs this radiation with an absorptance of 97.0 percent, so we don't lose our internal energy so quickly. How much power do we absorb when we are in a room where the temperature is 23.5 °C? How much energy does our body lose in one second?

The energy flux from the sun has a peak value of around 1500 W/m2, and solar cells are around 15% efficient. Estimate the area needed to satisfy US energy needs using solar cells, using the estimates that there are about 350 million people in the US and that we use an average of 90 kW/person. Also assume that there are about 6 hours of "peak" sunlight per day. Answer in square kilometers (do not put units in your answer, however).

A person is standing outdoors in the shade where the temperature is 33 °C. What is the radiant energy absorbed per second by his head when it is covered with hair? The surface area of the hair (assumed to be flat) is 170 cm2 and its emissivity is 0.85.

Consider a 260-m2 black roof on a night when the roof’s temperature is 27.5°C and the surrounding temperature is 12.5°C. The emissivity of the roof is 0.900. At what net rate does heat radiate, in kilowatts, from the roof?

A garage is illuminated by a single incandescent lightbulb dangling from a wire. If the bulb radiates light uniformly inall directions, and consumes an average electrical power of 50.0 W, what are (a) the average intensity of the light and(b) the rms values of E and B at a distance of 1.00 m from the bulb? (Assume that 5.00% of the electrical power consumed by the bulb is converted to light.)

A person is standing outdoors in the shade where the temperature is 33 °C.  The surface area of the hair (assumed to be flat) is 170 cm2 and its emissivity is 0.85. What would be the radiant energy absorbed per second by the same person if he were bald and the emissivity of his head were 0.65?

During the day, heat from the Sun is absorbed by the Earth’s surface.  (a)  Calculate the rate, in watts, at which this heat transfer through radiation occurs (almost entirely in the infrared) from 1.0 m2 to the atmosphere at night. Assume the emissivity is 0.90, the temperature of the surface of the Earth is 15°C, and that of outer space is 2.7 K.    (b)  The intensity of the Sun’s radiation at the Earth’s distance is about 800 W/m2, but only half of the incoming radiation is actually absorbed by the Earth’s surface. What fraction of the rate of radiation absorption by the Earth’s surface during the day is reemitted at night?  C.) What is the maximum magnetic field strength, in microteslas, of the outgoing radiation, assuming it is a continuous wave?

5. Calculate the total power radiated per unit area by a tungsten filament at a temperature of 3000. K. (Assume that the filament is an ideal radiator.) (b) If the tungsten filament of a lightbulb is rated at 75.0 W, what is the surface area of the filament? (Assume that the main energy loss is due to radiation.)

A hanging lamp with a 70-W omni-directional bulb has a hemi-spherical lamp shade of height, H = 0.55 m, as shown below. (a) Find the total (average) power received across the shade. W (b) Calculate the intensity at a point on the shade. W/m²