The Stefan-Boltzmann law relating energy per unit area F emitted by an object to its temperature T....?

Question

... temperature T, F=ϬT^4, is obeyed ideally by what type of object??

a) only hot gases, whose atoms emit and absorb only specific colors (e.g; neon tubes)

b) all objects, whatever their color or reflective properties

c) a red-colored object that absorbs blue light but reflects red light

d) a blackbody, a perfect absorber and emitter of energy at all wavelengths

a,b,c, or d?

Answer 1

basically the answer is (d) but i think i shall explain it more clearly

The Stefan-Boltzmann law, also known as Stefan's law, states that the total energy radiated per unit surface area of a black body in unit time j* is directly proportional to the fourth power of the black body's thermodynamic temperature T (also called absolute temperature):
j*=ϬT^4 j*=F
The irradiance j* has dimensions of power density (energy per time per square distance), and the SI units of measure are joules per second per square meter.
T is the kelvin. ε is the emissivity of the blackbody; if it is a perfect blackbody, ε = 1.

The law was discovered experimentally by Jožef Stefan (1835-1893) in 1879 and derived theoretically, using thermodynamics, by Ludwig Boltzmann (1844-1906) in 1884. Boltzmann treated a certain ideal heat engine with the light as a working matter instead of the gas. This law is the only physical law of nature named after a Slovene physicist.



(((((The law is valid only for ideal black objects, the perfect radiators, called black bodies.))))




given example should be considered for further explanation

Examples

Temperature of the Sun
With his law Stefan also determined the temperature of the Sun's surface. He learned from the data of Charles Soret (1854–1904) that the energy flux density from the Sun is 29 times greater than the energy flux density of a warmed metal lamella. A round lamella was placed at such a distance from the measuring device that it would be seen at the same angle as the Sun. Soret estimated the temperature of the lamella to be approximately 1900 °C to 2000 °C. Stefan surmised that ⅓ of the energy flux from the Sun is absorbed by the Earth's atmosphere, so he took for the correct Sun's energy flux a value 3/2 times greater, namely 29 × 3/2 = 43.5.

Precise measurements of atmospheric absorption were not made until 1888 and 1904. The temperature Stefan obtained was a median value of previous ones, 1950 °C and the absolute thermodynamic one 2200 K. As 2.574 = 43.5, it follows from the law that the temperature of the Sun is 2.57 times greater than the temperature of a lamella, so Stefan got a value of 5430 °C or 5700 K (modern value is 5780 K). This was the first sensible value for the temperature of the Sun. Before this, values ranging from as low as 1800 °C to as high as 13,000,000 °C were claimed. The lower value of 1800 °C was determined by Claude Servais Mathias Pouillet (1790-1868) in 1838 using the Dulong-Petit law. Pouilett also took just half the value of the Sun's correct energy flux. Perhaps this result reminded Stefan that the Dulong-Petit law could break down at large temperatures. If we collect the Sun's light with a lens, we can warm a solid to much higher temperature than 1800 °C.

Answer 2

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Answer 3

d. An oven with a small hole in the side approximates a black body radiator of the size of the hole, and this dodge is often used for physics experiments where you want black-body radiation.

Answer 4

Read the first sentence of this link:
http://en.wikipedia.org/wiki/Stefan_boltzmann_law