ëmax = 0.0029 / T
as the equation stands, it will
provide us with the wavelength in meters, not nanometers. Dividing 0.0029 by the value of
T specified in the question, 21000 K, we get ëmax = 0.000000138 meters. To change this
into nanometers, we note that there are 109 nanometers (1,000,000,000) in one meter. So
if the wavelength is 0.000000138 meters, we have to multiply that number by
1,000,000,000 to get the number of nanometers. It comes out as
ëmax = 138.1 nanometers.