how did federal power sharing become …

(i) Centre-State relations: As and when the ruling party at the State level was different, the parties that ruled at the Centre tried to undermine the power of the states. The Central Government has been misusing the Constitution to dismiss the State governments that were controlled by rival parties. This undermined the spirit of federalism. All this changed significantly after 1990. This period saw the rise of regional political parties in many states of the country.
(ii) Coalition Governments and autonomy of states: The era of coalition has changed the relationship between the centre and state governments since no single party got a clear majority in the LokSabha, the major national parties had to enter into an alliance with many parties including several regional parties to form a government at the Centre. This led to a new culture of power sharing and respect for the autonomy of State Governments.
(iii) Judgement of the Supreme Court: The Supreme Court of India has established strict guidelines for imposing President’s rule. With new guidelines it is very difficult for the Central Government to dismiss state governments in an arbitrary manner. Thus, federal power sharing is more effective today than it was in the early years after the Constitution came into force.

The speed of light in a medium depends on the properties of the medium. In electromagnetic waves, the speed is dependent on the optical density of the medium. Optical density is the tendency of the atoms in a material to restore the absorbed electromagnetic energy. The more optically dense material is, the slower the speed of light. One such indicator of the optical density of a medium is the refractive index.