An Electron in an Infinite Potential Well (A Box) Makes

Short Answer

An electron in an infinite potential well (a box) makes a transition from the n = 3 level to the ground state and in so doing emits a photon of wavelength 20.9 nm. (c = 3.00 × 10⁸ m/s, h = 6.626 × 10⁻³⁴J ∙ s, ^mel = 9.11 × 10⁻³¹ kg)
(a) What is the width of this well?
(b) What wavelength photon would be required to excite the electron from its original level to the next higher one?