Physics
A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is

Of higher pitch when train departs
The same in both cases in all respects
Of higher pitch when train arrives
Of higher intensity when train arrives

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Physics
What is refractive index ?

It is defined as the ratio of speed of light in vacuum to the speed of light in the medium.
It is defined as the ratio of speed of light in the medium to the speed of light in vacuum.
It is defined as the product of speed of light in medium and in vacuum.
None of above

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