Video Transcript
Which of the following types of
images are involved in the recording and playback of holograms? (A) Real images only, (B) virtual
images only, (C) both real and virtual images.
This question asks which images,
virtual or real, are used for the recording and playback of holograms. Let’s first consider the recording
of holographic images. The components of the apparatus
used for recording a holographic image are a coherent light source, a beam splitter,
plane mirrors, concave lenses, an object to be imaged, and a holographic plate. The holographic plate records the
interference pattern produced by coherent light from the object to be imaged and
coherent light from the coherent light source. We’ve seen that plane mirrors and
concave lenses are both used in producing holographic images. Neither of these components can
focus rays of light. This means that neither of them can
produce a real image. They only produce virtual
images.
Now, let’s consider the playback of
holographic images. A holographic plate on which an
image has been recorded is illuminated by a playback beam. The holographic plate diffracts the
playback beam, widening the beam. The light from the holographic
plate is not focused at a point and so does not produce a real image. This means that only virtual images
are used. The correct answer is option
(B).
