Due to the presence everywhere of the cosmic background radiation, the minimum p
ID: 2253493 • Letter: D
Question
Due to the presence everywhere of the cosmic background radiation, the minimum possible temperature of a gas in interstellar or intergalactic space is not 0 K but 2.7 K. This implies that a significant fraction of the molecules in space that can be in a low-level excited state may, in fact, be so. Subsequent de-excitation would lead to the emission of radiation that could be detected. Consider a (hypothetical) molecule with just one possible excited state.
(a) What would the excitation energy (in terms of
Explanation / Answer
a)the energy is
E = k x T
where k = 1.38 x 10^-23 J/K and T = 2.7 K
b)Also,we know that
E = (1/2)mv^2
or v^2 = (2E/m)
or v = (2E/m)^1/2
where m = 9.11 x 10^-31 kg
the wavelength of the photon is
L = h/mv
where h = 6.63 x 10^-34 J-s