As the wavelength of an electromagnetic (EM) wave becomes longer, its frequency decreases. This relationship is known as the inverse relationship between wavelength and frequency. In other words, when the wavelength of an EM wave increases, its frequency decreases, and vice versa.
This relationship can be understood by considering the wave equation for EM waves:
c = λν
Where c is the speed of light, λ is the wavelength, and ν (nu) is the frequency. Since the speed of light is constant in a given medium, any change in wavelength must be accompanied by a corresponding change in frequency to maintain the equation's balance.
For example, let's consider visible light, which is a form of EM radiation. Red light has a longer wavelength compared to blue light. Therefore, red light has a lower frequency than blue light. This is why we perceive red light as having a lower energy and appearing "warmer" than blue light, which has a higher frequency and higher energy.
In summary, as the wavelength of an EM wave becomes longer, its frequency decreases, resulting in a shift towards the lower end of the electromagnetic spectrum.