A video is taken of a road-sign mirage from the passenger seat in a car traveling at constant speed on a highway. The video spans the duration of seeing the mirage of the sign, viewing the vanishing of the mirage as the car approaches, and passing the road sign. The mirage angle, defined as the angle with respect to the horizontal at the moment…

In this paper we consider the main properties of cylindrical lenses and propose several demonstrational experiments that can be performed with them. Specifically we use simple glasses full of water to demonstrate some basic geometrical optics principles and phenomena. We also present some less standard experiments that can be performed with such…

Students often find the difference in the electromagnetic and the acoustic Doppler formulae somewhat puzzling. As is shown below, geometrical diagrams and the concept of "event"--a point in spacetime having coordinates (x,y,z,t)--can be a useful and simple way to explain the physical background behind the fundamental differences between the two…