# Waves
## A5 Fabry-Pérot Etalon
Consider two mirrors facing each other at a distance of $L$
**a)** What wavelengths of light would "fit" into this box?
**b)** What are the corresponding frequencies?
**c)** What are the corresponding photon energies?
**d)** In a universe where the speed of light was $\frac{c}{2}$ how would the three questions above change?
**e)** How could we use this setup to create a color spectrum of a test light source. You may vary any parameter given. (To put the light into the box we could use half transparent mirrors)
## A6 The flucto-harenaetic (wave-sand) effect
You want to prove that sandcastles attacked by waves act in the same way metals do when attacked by light.
Your hypothesis is that due to the quantum nature of waves (you have listened well to Prof Wörner) a sandcastle cannot be destroyed by too large waves, only by more energetic ones.
**a)** Describe the photoelectric effect, and how it was measured
**b)** How would you prove or disprove the flucto-harenaetic effect?
**c)** Using common sense describe the result of experiment b)
**d)** Explain the result. Why can/can't we describe the water wave using a quantum description?
## A7 Wave Particle Duality
You have learned in the course that particles can be described as waves.
**a)** How do we know this? And how can we calculate it?
**b)** A wave multicolored lightwave is diffracted by a single slit, which color component do you expect to be diffracted the most (or which color does the edge of the spot have?)
**c)** What is the length of a sound wave at 16 Hz. Remember that to find the distance between you and a thunderstorm you divide the time in seconds by three and get the distance in kilometers.
**d)** Why can we hear around corners, but not see around corners?
**e)** The wavelength of a particle is given by its momentum, why do we not see macroscopic objects, which are still ($p =0$) behave as waves?