Imagine a particle that has three times the mass of the electron. All other quantities given above remain the same. What is the ratio of the kinetic energy KheavyKheavyK_heavy that this heavy particle would have when it reaches the upper plate to the kinetic energy KeKeK_e that the electron would have? That is, what is KheavyKeKheavyKe?

it would be kevlar ^^

snell's law

refractve index = sin incidence / sin refraction

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m