Some Queries...

1) A sample of ¹⁴CO₂ was mixed with ordinary ¹²CO₂ for some expt. 10 ml. of this mixture at STP possesses the rate of 10⁴ Disintegrations per min. How many milli-curie of radio-active carbon is reqd to prepare 60lt. of such a mixture?

2) Rutherford's scattering formula fails for very small angles because (multi-correct type).

i) The full nuclear charge of the target atom is partially screened by it's electron.
ii) Impact parameter between the alpha particle source and the nucleus of the target is very large compared to the size of the nucleus.
iii) K.E. of the alpha particle is very large.
iv) Gold foil is very thin.

3) Which is/are correct?
i) ²³⁸U has a small cross section for the capture of a slow neutron.
ii) ²³⁵U has a very large cross-section for the capture of slow neutrons.
iii) Neutrons are accelerated by moderators.
iv) All of the above.