To what temperature must we heat an object until its peak thermal radiation is in the red region of the spectrum (λ = 650 nm)?

• The wavelength of the thermal radiation coming from an object can be calculated by assuming the object to be a blackbody. A blackbody is an ideal object that absorbs all the radiation that falls on it.

• The maximum wavelength emitted by a blackbody is given by Wien's displacement law. It states that the black-body radiation curve for different temperatures will peak at different wavelengths that are inversely proportional to the temperature.

• The peak wavelength emitted by a blackbody is given by,

$\boxed{{\mathbf{\lambda }}_{\mathbf{m}\mathbf{a}\mathbf{x}}\mathbf{=}\frac{\mathbf{2898}\mathbf{\text{ μm}}\mathbf{\cdot }\mathbf{\text{K}}}{\mathbf{T}}}$

Here T is the absolute temperature of the object.