Iona and Peter Opie observe in The Classic Fairy Tales (1974), that Jack's coat may have been borrowed from the Tale of Tom Thumb or from Norse mythology, but they also draw comparisons with the Celtic stories of the Mabinogion. In the English fairy tale Jack the Giant Killer, the hero is rewarded with several magical gifts by a giant he has spared, among them a coat of invisibility. A similar mantle appears in the Second Branch of the Mabinogi, in which it is used by Caswallawn to assassinate the seven stewards left behind by Bran the Blessed and usurp the throne. The mantle is described again, and in more detail, in the Breuddwyd Rhonabwy, and is later listed as one of the Thirteen Treasures of the Island of Britain. Such cloaks are common in Welsh mythology a 'Mantle of Invisibility' is described in the tale Culhwch and Olwen (c. 1100) as one of King Arthur's most prized possessions. The motif falls under 'D1361.12 magic cloak of invisibility' in the Stith Thompson motif index scheme.Ĭloaks of invisibility are magical items found in folklore and fairy tales. It is a common theme in Welsh and Germanic folklore, and may originate with the cap of invisibility seen in ancient Greek myths. In folklore, mythology and fairy tales, a cloak of invisibility appears either as a magical item used by duplicitous characters or an item worn by a hero to fulfill a quest. So.Alberich puts on the Tarnkappe and vanishes illustration by Arthur Rackham to Richard Wagner's Das RheingoldĪ cloak of invisibility is an item that prevents the wearer from being seen. Separate the two sets according to the formula* so that the two f2 lenses are d2 apart. In this case, with my lenses from the kit: Separate F1 from F2 by the sum of their focal lengths to arrive at d1, the distance between the two lenses in each set. But really - any two positive focal lengths will do. For the lenses i have from the KIT I bought, the focal lengths are 50mm and 150mm - this makes it so the entire set up fits neatly on a single meter stick. Start with 2 sets of lenses with different focal lengths. The distances between the lenses and the sets of lenses depends on the focal lengths of the lenses you start with and is defined by some simple math: Then each “set” is set at a distance from the other (d2). Each “set” is composed of two lenses (f1 and f2 ) at a distance from one another (d1). The trick is setting up the lenses at specific distances from each other along an axis (meter stick)īy setting up the four lenses as shown you can create cloaked regions.

This project uses 4 simple lenses, a meter stick and some very simple math to create regions of invisibility. One way to achieve invisibility is to bend light (refraction) around an object - one way to do that is with lenses. What really mean is that we are able to see around and behind the invisible object, as though it were not there at all. Now, you can simply cover an object and no light from it will get into your eye, but that is not really invisibility in the way that we like to think about it.

The object is present, but no light bounces from it into your eye, so it appears to “not be there”. Invisibility happens when an object that “should” bounce light into your eye does not. This is a replica of the Rochester Cloak - developed last year at the University of Rochester in NY. Okay - its not a CLOAK, per se, but it is a cloaking technology - and its a super simple set up to see how one of the most promising approaches to invisibility technology that we can use (think surgeons being able to see through their hands during surgery).

Invisible cloak project