-->

Atoms

Question
CBSEENPH12039606

Suppose an electron is attracted towards the origin by a force k/r where ‘k’ is a constant and ‘r’ is the distance of the electron from the origin. By applying Bohr model to this system, the radius of the nth orbital of the electron is found to be ‘rn’ and the kinetic energy of the electron to be Tn. Then which of the following is true?

  • Tn ∝ 1/n2, rn ∝ n2 

  • Tn independent of n, rn ∝ n

  • Tn ∝ 1/n, rn ∝ n 

  • Tn ∝ 1/n, rn ∝ n2

Solution

B.

Tn independent of n, rn ∝ n

straight k over straight r space equals space mv squared over straight r
mv squared space equals space straight k space space left parenthesis independent space or space straight r right parenthesis
straight n open parentheses fraction numerator straight h over denominator 2 straight pi end fraction close parentheses space equals space mvr
rightwards double arrow space straight r proportional to space straight n
and space straight T space equals space 1 half mv squared space space is space independent space of space straight n.