Assuming a filament in a 100 W light bulb acts like a perfect blackbody, what is

Question

Assuming a filament in a 100 W light bulb acts like a perfect blackbody, what is the temperature of the hottest portion of the filament if it has a surface area of 6.3 times 10^-5 m^2? The Stefan-Boltzmann constant is 5.67 times 10^-8 W/(m^2 K^4). 130 K 2300 K 30, 000K 1100 K 5800 K A UFO files directly over a football stadium at a speed of 0.50c. If the proper length of the field is 100 yards, what field length is measured by the crew of the UFO? 59 yards 87 yards 121 yards 75 yards 113 yards A bomb is designed to explode 2.00 s after it is armed. The bomb is launched from earth and accelerated to an unknown final speed. After reaching its final speed, however, the bomb is observed by people on earth to explode 4.25 s after it is armed. What is the final speed of the bomb just before it explodes? 0.995c 0.939c 0.882c 0.971c 0.904c Determine the speed at which the kinetic energy of an electron is equal to twice its rest energy. 0.45c 0.87c 0.99c 0.63c 0.94c The position of a hydrogen atom (m = 1.7 times 10^-27 kg) is known to within 2.0 times 10^-6 m. What is the minimum uncertainty in the atoms velocity? zero m/s 0.011 m/s 0.031 m/s 0.0085 m/s 0.016 m/s A laser emits a single, 2.0-ms pulse of light that has a frequency of 2.83 times 10^11 Hz and a total power of 75, 000 W. How many photons are in the pulse? 8.0 times 10^23 2.4 times 10^25 4.0 times 10^26 81.6 times 10^24 3.2 times 10^25 When ultraviolet photons with a wavelength of 3.45 times 10^-7 m are incident on an unknown metal surface in a vacuum, electrons with a maximum kinetic energy of 1.52 eV are emitted from the surface. What is the work function of the metal? 3.60 eV 2.59 eV 1.98 eV 3.11 eV 2.08 eV

Explanation / Answer

12. The Stefan–Boltzmann law states that the power emitted per unit area of the surface of a black body is directly proportional to the fourth power of its absolute temperature.

P/A=sigmaT^4

P=100, A=6.3X10^-5,sigma=5.67x10^-8.

T=2300K

16. delta v = (hbar/2)*(1/m*del x)

delta v= .016m/sec

17. Power=Energy/time = number of photons*h*frequency/time = 75000

So, number of photons=8x10^23

18. 1.52ev + work function=hv

Work function = 3.6-1.52 = 2.08eV

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