Light traveling through air at 3.00 · 108 m/s. reaches an unknown medium and slows down to 2.00 · 108 m/s. what is the index of refraction of that medium

Hydrogen atoms are excited by a laser to the =4n=4 state and then allowed to emit. what is the maximum number of distinct emission spectral lines (lines of different wavelengths) that can be observed from this system? 8 6 2 7 4 5 1 3 calculate the wavelength of the 4⟶14⟶1 transition. =λ=