# Question: A 100 W incandescent light bulb bas a cylindrical tungsten filam

A 100-W incandescent light bulb bas a cylindrical tungsten filament 30.0cm long, 0.40 mm in diameter, and with an emissivity of 0.26.

(a) What is the temperature of the filament?

(b) For what wavelength does the spectral emittance of the bulb peak?

(c) Incandescent light bulbs are not very efficient sources of visible light. Explain why this is so.

(a) What is the temperature of the filament?

(b) For what wavelength does the spectral emittance of the bulb peak?

(c) Incandescent light bulbs are not very efficient sources of visible light. Explain why this is so.

## Answer to relevant Questions

The shortest visible wavelength is about 400 run. What is the temperature of an ideal radiator whose spectral emittance peaks at this wavelength?Show that for large values of A the Planck distribution, Eq. (38.32), agrees with the Rayleigh distribution, Eq. (38.31). A 2.50-W beam of light of wavelength 124 nm falls on a metal surface. You observe that the maximum kinetic energy of the ejected electrons is 4.16eV. Assume that each photon in the beam ejects a photoelectron. (a) What is ...A large number of hydrogen atoms are in thermal equilibrium. Let n2/n1, be the ratio of the number of atoms in an n = 2 excited state to the number of atoms in an n = 1 ground state. At what temperature is n2/n1 equal to (a) ...Nuclear fusion reactions at the center of the sun produce gamma-ray photons with energies of order 1 MeV (106eV). By contrast, what we see emanating from the sun's surface are visible light photons with wavelengths of order ...Post your question