2. (a) The interstellar gas (i.e. the gas between stars) has temperature 80 K and consists of 104 hydrogen atoms m-³; the diameter of a H atom is approximately 10-¹0 m.Estimate (1) the mean free path of a H atom in interstellar space and (2) the mean time between collisions. (b) In reality, the interstellar gas actually consists of a mixture of H atoms (104 m-³)and He atoms (10³ m-³).Since this is case, what is the pressure in the interstellar gas if it has temperature of 80 K?

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