### Mensuration & Hologram

When 4 trapeziums are joined together to form a 3D object - it looks like a square-base pyramid without the "tip" is called a truncated square pyramid.

You can make a hologram out of this when it's created with transparent sides.
From wikipedia (15 August 2015):
Holography is the science and practice of making holograms. Normally, a hologram is a photographic recording of a light field, rather than of an image formed by a lens, and it is used to display a fully three-dimensional image of the holographed subject, which is seen without the aid of special glasses or other intermediate optics. The hologram itself is not an image and it is usually unintelligible when viewed under diffuse ambient light. It is an encoding of the light field as an interference pattern of seemingly random variations in the opacity, density, or surface profile of the photographic medium. When suitably lit, the interference pattern diffracts the light into a reproduction of the original light field and the objects that were in it appear to still be there, exhibiting visual depth cues such as parallax and perspective that change realistically with any change in the relative position of the observer.

What you need:
• A sheet of transparency - that will form the pyramid
• A graph paper - to draw the trapezium with exact dimensions
• Scissors, Tape, Marker
• Online resources
Step 1: draw a trapezium with dimensions as shown below:

Step 2: Trace the trapezium onto the transparency. You will need 4 identical trapeziums.

Step 3: Cut the trapeziums and tape them together (along the slant edges) as shown.

Step 4: Place the inverted truncated square pyramid on the screen as shown

Step 5: Now, play the clip against a dark background.

Online resource:
Hologram video (you can search for "hologram video" at Youtube)
Here's an example:
Enlarge it to full screen and place your frame at the centre (with reference to the cross)