Determine the wavelength of incident electromagnetic radiation required to cause an electron transition from the n = 5 to the n = 7 level in a hydrogen atom.

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

A36,287 kg truck has a momentum of 907,175 kg • . what is the truck’s velocity

What is reflection, what is refraction, and what is diffraction. what some similarities or differences between the three.