Physics
What is refractive index ?

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

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Physics
Holography is a technique of

Recording a permanent three dimensional black and white photograph
Recording a permanent three dimensional photograph of a given single colour or a multicolour
Recording a permanent three dimensional multicolour photograph
Recording a permanent, sharp two diimensional black and white or multicolour photograph

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