Work out wien displacement law instantly with clear inputs, formula shown and shareable results.
Wien's displacement law puts the peak of a black body's spectrum at lambda = 2.898e-3/T metres. The Sun's 5778 K photosphere peaks at 501 nm, in the green - which is why our vision is centred there. A 300 K room peaks at 9.7 microns, deep in the infrared where thermal cameras operate.
Wien's displacement law
lambda(peak) = 2.8978e-3 / T
Frequency form
f(peak) = 2.8214 k T / h
Because they peak in different spectral densities - per unit wavelength versus per unit frequency. Converting one peak into the other is not valid.
Around 1000 K the peak is at 2.9 microns but the visible tail is red. Metal glows visibly red from about 800 K.