Physics
Holography is a technique of

Recording a permanent three dimensional multicolour photograph
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, sharp two diimensional black and white or multicolour photograph

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Physics
The blue colour of water in the sea is due to

Reflection of blue light by impurities in sea water
Reflection of blue sky by sea water
Absorption of other colours except blue by water molecules
Scattering of blue light by water molecules

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