The Total solution for NCERT class 6-12
If Bohr’s quantisation postulate(angular momentum = nh/2π) is a basic law of nature, it should beequally valid for the case of planetary motion also. Why then do we never speakof quantisation of orbits of planets around the sun?
We never speak of quantization oforbits of planets around the Sun because the angular momentum associated withplanetary motion is largely relative to the value of Planck’s constant (h).The angular momentum of the Earth in its orbit is of the order of 1070h.This leads to a very high value of quantum levels n of theorder of 1070. For large values of n, successiveenergies and angular momenta are relatively very small. Hence, the quantumlevels for planetary motion are considered continuous.