Hello Luna!
Remember, any time you see the unit Hz (read as Hertz), it is a unit of frequency (ν). The units of frequency are s-1. MHz in this case is short for MegaHertz.
The frequency for a 99MHz radio wave IS 99 MHz, or in SI units, 9.9 x 107 Hz (multiply 99 by 106; you can find this conversion online).
To find the wavelength you need to remember that frequency (v), wavelength(λ) , and the speed of light "c" are related by this equation: c = vλ. Because we know the value of "c" (3 x 108 m/s; a universal constant), and we just found frequency (v), we can rearrange the equation above to solve for wavelength. Stick to SI units when doing these calculations!
λ = c / v
Wavelength λ = (3 x 108 m/s) / (9.9 x 107 Hz) = 3.03 m
Let's quickly check our work. Notice how the units cancel out when we perform this operation. We know that wavelength needs to have a unit of, well, length! In SI units, meters is the preferred unit of length.
(m/s) divided by (1/s) surely gives m, which is a unit of length.
Pretty amazing right? FM radiowaves have a wavelength that is about as long as the arm span of almost two people!
To find the energy (E) of this wave simply use the relation that the energy is related to its frequency times a constant; E = hv. The "h" in this case is a universal constant called Planck's constant (6.63 x 10-34)
E = hv = (6.63 x 10-34) x (9.9 x 107 Hz) = 6.56 x 10-26 J
The units, although a little more complex here, still give the answer in a unit of energy, so this answer makes sense! According to our results, although these waves do not contain much energy, it is just enough to make our car rides enjoyable!
If you would like more help with waves, or chemistry/physics in general, feel free to schedule an appointment with me! Thanks for reading!
