I have a question which is: The filament of a 40W light bulb has a radius of 1.5μm and a length of 10cm. Estimate: i) the operating temperature of the filament ii) the peak wavelength of the emitted thermal radiation Stating any assumptions made. I assumed that the filament was made of tungsten and has an emissivity of 0.26. I then used the forumla: H = AeσT^4 but this gave me a temperature of 139972.5K, which as far as I'm aware is hotter than the surface temperature of the sun right? For the second part of the question, I wanted to use E=mcΔθ to get the energy, and then use this with E=hf to find the frequency and thus be able to calculate the wavelength. However after further consideration I decided against this idea, as I don't have a change in temperature, only a single value (and the lack of specific heat capacity of tungsten in the question also lead me to think that this wasn't the best course of action to take). Any help would be greatly appreciated.