Prove with help of postulate of Bohr's theory that the velocity of an electron revolving in the first orbit of a hydrogen- like atom or ion is double of that revolving in the second orbit .

Explanation

According to the postulate of Bohr's theory , velocity of an electron revolving in the nth orbit of a hydrogen like atom or ion `v_(n) = (3pi Z e^(2))/(nh)`
For first orbit , the velocity `v_(1) = (2 pi Z e^(2))/(n) [ because n = 1]`
For second orbit , the velocity `v_(2) = (2pi Z e^(2))/(2h) [ because n = 2]`
`therefore v_(2) = (1)/(2) v_(1) or v_(1) = 2 v_(2)`