Acommon radio wavelength observed coming from astronomical objects is 21 cm. what temperature is associated with this radiation?

The temperature associated with this radiation is 0.014K.

Explanation:

If we assume that the astronomical object behaves as a black body, the relation between its wavelength and temperature is given by Wien's displacement law.

where,

λmax is the wavelength at the peak of emission

b is Wien's displacement constant (2.89×10⁻³ m⋅K)

T is the absolute temperature

For a wavelength of 21 cm,

first one is the correct answer

a:

by the combination of an unlimited number of elements