A light bulb radiates most strongly at a wavelength of about 3000 nanometers. How hot is its filament?

1000K

To determine the temperature of the filament of a light bulb, we can use Wien's Displacement Law, which relates the peak wavelength of radiation emitted by an object to its temperature.

Wien's Displacement Law states that the peak wavelength (λ_max) multiplied by the temperature in Kelvin (T) is equal to a constant value (b):

λ_max * T = b

The constant value (b) is approximately equal to 2.9 x 10^(-3) meters * Kelvin.

Given that the peak wavelength of the light bulb is 3000 nanometers (or 3000 x 10^(-9) meters), we can rearrange the equation to solve for the temperature (T):

T = b / λ_max

T = (2.9 x 10^(-3)) / (3000 x 10^(-9))

T ≈ 966.7 Kelvin

Therefore, the temperature of the filament of the light bulb is around 966.7 Kelvin.

The Wien displacement law will tell you it is about 1000 K. Actually, the filament of a tungsten lamp is hotter than that-- more like 2500 K. The emissivity changes with wavelength. I do not believe their statement about the wavelength of maximum emission. Perhaps they are counting the radiation from the glass, which domimates at 3000 nm.