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When a photograph is cut in half, each bit shows half of the scene. When a hologram is cut in half, the whole scene can nonetheless be seen in every bit.
One can see all the same issues via the smaller window (by moving the head to vary the viewing angle), but the viewer can see extra without delay via the 120 cm (four ft) window. A photograph could be considered in a wide range of lighting situations, whereas holograms can only be considered with very specific forms of illumination. A lens is required in pictures to record the image, whereas in holography, the light from the object is scattered directly onto the recording medium.
This allows the scene to be viewed from a range of different angles, as if it have been nonetheless present. When the 2 laser beams reach the recording medium, their light waves intersect and intrude with one another. It is that this interference pattern that's printed on the recording medium. The pattern itself is seemingly random, because it represents the best way during which the scene's light interfered with the original mild source – however not the original gentle source itself. The interference pattern can be thought-about an encoded model of the scene, requiring a particular key – the original light supply – so as to view its contents.
A photograph could be recorded utilizing normal gentle sources (daylight or electrical lighting) whereas a laser is required to document a hologram. A hologram represents a recording of data regarding the light that got here from the original scene as scattered in a variety of instructions somewhat than from just one path, as in a photograph.
This is as a result of, whereas each point in a photograph solely represents mild scattered from a single point within the scene, every point on a holographic recording includes details about gentle scattered from every point within the scene. It can be thought of as viewing a avenue outdoors a home through a a hundred and twenty cm × one hundred twenty cm (4 ft × 4 ft) window, then through a 60 cm × 120 cm (2 ft × four ft) window.