Video Transcript
The diagram shows some apparatus
used in holography, including a cylindrical object. Which of the following is the term
used to describe the beam that follows the path capital 𝐵, capital 𝐶 and capital
𝐵, capital 𝐷? (A) Virtual beam, (B) image beam,
(C) object beam, (D) illumination beam, (E) reference beam.
Let’s begin by identifying this
beam on our diagram. We see that point 𝐵 on our diagram
is here and the beam that goes from capital 𝐵 to capital 𝐶 and capital 𝐷 is this
one here. This is all the same beam. The light that is reflected off of
this mirror passes through a prism so it spreads out. We see that this beam comes from
point 𝐴 on our diagram and ultimately comes from our laser light source. It never interacts then with the
object that we’re looking to make a hologram of. Despite that fact, this beam is
vital to creating a hologram because it provides a standard or a reference for the
beam that does indeed interact with our object.
In making a hologram, the idea is
that a beam that interacts with the object of interest and a beam that doesn’t
interfere with one another. When they do, a three-dimensional
image, a hologram, is created of the object. As we’ve seen, the beam from
capital 𝐵 to capital 𝐶 and capital 𝐷 is a reference. We could think of it as a standard
or a baseline against which to compare the light that does interact with our
object. The term used to describe this beam
is reference beam. We choose answer option (E).
Let’s look now at part two of our
question.
Which of the following is the term
used to describe the beam that follows the path lowercase 𝑏, lowercase 𝑐, capital
𝐶 and lowercase 𝑏, lowercase 𝑑, capital 𝐷? (A) Object beam, (B) reference
beam, (C) virtual beam, (D) image beam, (E) Illumination beam.
Whereas before we were talking
about the beam of light that doesn’t interact with our object, now we’re talking
about the beam that does. This beam is identified as the one
that goes from lowercase 𝑏 to lowercase 𝑐 to uppercase 𝐶 and from lowercase 𝑏 to
lowercase 𝑑 to uppercase 𝐷. This is one beam. And as we see, it bounces off of
the object and then reaches this last component in our diagram. The fact that this beam does
interact with the object is what gives it its name. It’s called the object beam.
Interestingly, the object beam by
itself is not enough to create a hologram of our object of interest. The object beam and the reference
beam must interfere with one another to make the hologram. In any case, for our answer, we
choose option (A). The term used to describe the beam
that follows the path lowercase 𝑏, lowercase 𝑐, uppercase 𝐶 and lowercase 𝑏,
lowercase 𝑑, uppercase 𝐷 is object beam.
