Wavelength, period and frequency are closely related to each other. By definition, wavelength is just the distance between two identical points in the adjacent cycles of a wave, and period is the time it takes to complete one cycle of the wave. Frequency is then the number of cycles in a second. In other words, frequency is the inverse of period, frequency = 1 / period.      Besides this, c = λ × f. Where λ refers to wavelengh, while f refers to frequency. c can be either speed of sound, speed of light, etc.      Generally, we don't talk about period when dealing with energy. Wavelength and frequency are what we deal with here because they are in the formula of energy. Energy E = h * f or E= h * c / λ . These two equations are equivalent because frequency = speed of light / wavelength  when we talk about electromagnetic waves. Notice that all electromagnetic waves travel at the speed of light, and that is why c refers to speed of light here. The h in the fomula refers to the Plank's Constant. Most of the time the frequency f has a different notation which looks like v, but since I can't type it here, I use f instead. E = h * f is the Planck Relation, and sometimes it is also known as the Planck–Einstein Equation. From the relationships we go over above, we can conclude that long wavelengh means lower energy, while higher frequency means higher energy. This is easy to explain. Since c = λ × f, wavelength λ and frequency f  are in inverse proportion.