If you increase the wavelength of electromagnetic radiation too much, such that the frequency approaches zero, or if you try to make the frequency infinite, you enter theoretical limits and encounter certain consequences:
Frequency approaching zero (wavelength approaching infinity): As the wavelength of electromagnetic radiation approaches infinity, the frequency tends toward zero. In this limit, the electromagnetic waves become more like static electric or magnetic fields. They no longer exhibit the oscillating behavior typically associated with waves. Instead, you have a constant electric or magnetic field that does not change with time. This is often referred to as the "DC" (direct current) limit, where "DC" stands for "direct current."
Frequency approaching infinity (wavelength approaching zero): As the wavelength of electromagnetic radiation approaches zero, the frequency increases toward infinity. In this limit, the behavior of electromagnetic waves becomes increasingly difficult to describe within classical physics. Quantum mechanical effects become significant, and the wave-particle duality of light becomes apparent. At extremely high frequencies, electromagnetic radiation starts to exhibit particle-like behavior, and the discrete nature of energy quanta called photons becomes more pronounced. The description of such radiation requires the framework of quantum electrodynamics.
It's important to note that these limits represent extreme theoretical cases, and in practice, electromagnetic radiation spans a wide range of frequencies and wavelengths. From radio waves with long wavelengths and low frequencies to gamma rays with short wavelengths and high frequencies, each region of the electromagnetic spectrum has its own unique properties and applications.