(a) Use Stefanâs law to calculate the total power radiated perunit area by a tungsten filament

at a temperature of 3000 K. (Assume that the filament is an idealradiator.) (b) If the tungsten

filament of a light bulb is rated at 75 W, what is the surface areaof the filament? (Assume

that the main energy loss is due to radiation.)

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Compute the wavelength of light that has the maximum intensity for the light bulb described in the previous problem( The previous problem was: Estimate the surface area of the tungsten filament of a 100-Wlight bulb if the filament is heated to 2500 K (Kelvin)) consider now making a beam of photons at this same wavelength. How many photons per second will be in the beam assuming the total power is 100 W, as is the case of the light bulb? Please show you work and explain in details?

The tungsten filament of an incandescent light bulb hasatemperature of approximately 3000 K. The emissivity of tungstenisapproximately 1/3, and you may assume that it is independentofwavelength.
(a). If the bulb gives off a total of 100 watts, what is thesurfacearea of its filament in square millimeters?
(b). At what value of the photon energy does the peak in thebulb'sspectrum occur? What is the wavelength corresponding to thisphotonenergy?
(c). Sketch the spectrum of light given off by thefilament.Indicate the region on the graph that corresponds tovisiblewavelengths, between 400 and 700 nm.
(d). Calculate the fraction of the bulb's energy that comes outasvisible light. (Do the integral numerically on a calculatororcomputer.) Check your result qualitatively from the graph ofpart(c).
(e). To increase the efficiency of an incandescent bulb, wouldyouwant to raise or lower the temperature?
(f). Estimate the maximum possible efficiency (i.e. fractionofenergy in the visible spectrum) of an incandescent bulb, andthecorresponding filament temperature. Neglect the fact thattungstenmelts at 3695 K.

The surface temperature of our Sun is about 5800K. Assuming that it acts as a blackbody:

(a) What is the power flux radiated by the Sun, in W/m²?

(b) If the surface area of the Sun is 6.087 x 10¹²m², what is the total power emitted in watts?

(c) Because watts are .I/s, how many joules of energy are radiated in one year ( 365 days)? (Note: The Sun is actually a very poor approximation of a blackbody.)

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