EM waves can vary greatly in size. How long can they be at the highest frequencies?

Electromagnetic (EM) waves span a broad range of wavelengths, which correspond to different frequencies. At the highest frequencies, such as gamma rays, the wavelengths are extremely short, often measuring just a fraction of the size of an atom. In fact, gamma rays can have wavelengths shorter than 0.01 nanometers, which is significantly less than the width of an atom.

Therefore, the option stating that EM waves can be "thousands of miles" long is not true in the context of the highest frequencies, as these are characterized by very short wavelengths. Instead, at these frequencies, the typical wavelengths are not only shorter than the width of an atom but are in the range that extends into the quantum scale. This illustrates how electromagnetic waves can behave uniquely across the spectrum, particularly when discussing their wavelengths at high frequencies.