An electron is trapped in a one‑dimensional box that is 476 nm wide. Initially, it is in the n = 4 energy level but, after a photon is absorbed, the electron is in the n = 8 energy level. What was the wavelength of the absorbed photon?

Explanation:

Below is an attachment containing the solution

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me