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

ANSWER DOWNLOAD EXAMIANS APP

Physics
Railway tracks are banked on curves so that

The train may not fall down inwards
Necessary centrifugal force may be obtained from the horizontal component of the weight of the train
Necessary centripetal force may be obtained from the horizontal component of the weight of the train
No frictional force may be produced between the tracks and the wheels of the train

ANSWER DOWNLOAD EXAMIANS APP