FYKOS Year 33 Series 4 Problem 4 — optical FYKOS bird · FYKOS 33 #33.4.4
Physics · optics
Problem
The FYKOS bird found an optical bench at the Faculty of Physics. The bench allows him to place different tools along an optical axis.
He started to play with it and gradually placed onto it: a point source of light, a first lens, a second lens and a screen, with the same
spacing between them (so the distance between the screen and the light source is three times bigger than any distance of two
neighbouring tools). A sharp image of the source was created on the screen. Then, he dipped the whole system into an unknown liquid,
which he found in a strange container. To his amazement, the image on the screen stayed sharp. Figure out the refractive index of the given liquid,
which is certainly different from the refractive index of air. You can assume that the refractive index of air is unitary. One of the lenses
has ten times bigger focal length than the other and both are thin, manufactured from a material with refractive index 2.