Narrow-Band Invisibility Cloaking: The Vanishing Test Tube Revisited

Invisibility has long been a staple in science fiction. The idea of not being seen has enchanted people for centuries. Recent examples in popular literature include H. G. Wells’s The Invisible Man, Wonder Woman’s invisible plane, and the invisibility cloak featured in several Harry Potter books. While advances in optical cloaking have improved the likelihood of realizing invisibility, classroom demonstrations involving a vanishing object immersed in a liquid have been popular with students and teachers alike. In these demonstrations, the refractive indices of the materials and liquid are very close, and the invisibility effect is observed using white light or a broadband light source. However, since the index of refraction is a function of wavelength, any dependence of invisibility on wavelength would not be observed.