Answer:
75 W
Explanation:
[tex]T[/tex] = temperature of the filament = 2100 K
[tex]A[/tex] = Emitting area of the filament = 1 cm² = 10⁻⁴ m²
[tex]e[/tex] = Emissivity = 0.68
[tex]\sigma[/tex] = Stefan's constant = 5.67 x 10⁻⁸ Wm⁻²K⁻⁴
Using Stefan's law, Power output of the light bulb is given as
[tex]P = \sigma e AT^{4} \\P = (5.67\times10^{-8}) (0.68) (10^{-4}) (2100)^{4}\\P = 75 W[/tex]
