A ball is thrown vertically upwards. The ball spends a time of 4.6 s in the air, before landing at the same point from where it was thrown. With what initial speed was the ball thrown?

An observer that stands still as the electron moves by him, will observe

Which type of wave can travel without a medium

Exercise 2. find the wavelength of a photon emitted when an electron jumps from the n = 3 energy level down to the n = 2 energy level. where is this photon in the electromagnetic spectrum?