Consider a transition at 5000 Å with a width of 1 Å and a cavity 2 cm3 in volume. How many electromagnetic modes exist in this frequency band for this cavity?

An electron moves with a constant horizontal velocity of 3.0 × 106 m/s and no initial vertical velocity as it enters a deflector inside a tv tube. the electron strikes the screen after traveling 26 cm horizontally and 19 cm vertically upward with no horizontal acceleration. what is the constant vertical acceleration provided by the deflector? (the effects of gravity can be ignored.)