The Crab Nebula is a cloud of glowing gas located about 6500 light years away. Viewing from the Earth, its apparent visual brightness is only of our Sun (the solar luminosity is W, and the distance of the Sun is about m). Astronomers estimate that the power observed in visual wavelengths only accounts for about 1/100 of the total power needed for energizing the Crab Nebula. Estimate the total power needed for energizing the Crab Nebula (in Watts). g

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m