Magic Arcs

The two semi-circular arcs when placed one above the other creates an optical illusion that makes the lower arc appear bigger than the upper one. This is one of the very easy and most practiced tricks that are generally displayed by kids to baffle friends.

Magic is all about creating illusion and the concepts of physics and chemistry are utilized by the magicians all over the world to create confusion in the minds of the people. Optical illusion can be created using the concepts like refraction, dispersion and many others that make the objects appear different in shape and size from the original.

How to perform Magic Arcs:

Performing magic arcs are made effective with the use of two semi-circular arcs of different colors.

1. It begins by choosing two arcs of contrasting colors. They are arranged one above the other, closer to each other by holding them in the air. Say, yellow arc at the bottom of the red.

2. Yellow arc appears larger than the red one. This works on the basis of the principle that when one semicircular segment is placed inside the circle, the segment appears larger than the corresponding portion of the outer circle.

3. The trick can be made more convincing by altering the position of the arcs and by pretending to stretch the smaller appearing arc.

4. The lower arc will always appear larger than the upper one.

Related experiments to magic arcs :

The same trick can be made funnier with the help of bananas. The trick is known as stretching bananas.  In this trick also, the two bananas are kept side by side and the spectators are made to believe that one of them is smaller in size which is actually not. Then you pretend to stretch smaller banana to bring it at par with the larger banana. This activity is interesting enough to keep the audience engaged.

Portraits on dollar bill can be made to express emotions like small and frown on the face of George printed in the bill. The secret lies in folding the bill in such a way that creases made on the bill are able to create an optical illusion that resembles some or the other expression on the face.

The optical illusion is a sure shot way to device interesting tricks that can keep the audience enthralled. Many games available in the market are believed to be based on this phenomenon. So, next time when the kid is about to take out something interesting from his magic box, you will be able to know the concept behind it.

Logic behind the activity:

Eyes compare the outer larger rim of the lower arc with the smaller portion of the /above arc, thus leaving an impression that the arc placed below is larger than the upper one.


Tricks like magic arcs are easy to perform and are able to provide a different insight to the understanding of science concepts. Similar tricks in the form of kits are available online at reasonable price. So next time before jumping on the other gaming options, it is advisable to take a tour to the sites that offer magic kits for the children.

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