Given de- Broglie's explanation of quantisation of angular momentum as proposed by Bohr.

State the law of conservation of angular momentum.

Write the de Broglie's equation.

Define angular momentum of a rigid body.

Define torque and angular momentum .

de-Broglie equation is

Orbital angular momentum depends upon

(a) Using Bohr's second postulate of quantization of orbital angular momentum, show that the circumference of the electron in the nth orbital state in hydrogen atom is n times the de-Broglie wavelength associated with it. (b) The electron in hydrogen atom is initially in the third excited state. What is the maximum number of spectral lines which can be emitted when it finally moves to the ground state ?