Diffraction of Electromagnetic Waves from a Round Hole Located between Vacuum and Matter with a Refraction Index Different from One

The diffraction of an electromagnetic wave from a round hole on an opaque screen is studied when there is no vacuum on the opposite sides of the screen, as is usually considered, but on one side there is a refractive medium and on the other—vacuum. The diffraction peculiarities due to the fact that the medium into which the wave penetrates from the vacuum have a refractive index different from one are revealed. The case of diffraction in an anisotropic medium with the property of birefringence is also considered.