Yes, the Planck constant "h" applies to electromagnetic waves of all frequencies, including low and ultra-low frequency waves. The Planck constant is a fundamental constant in quantum physics and is used to relate the energy of a photon to its frequency. It is used in the equation:
E = h * f
where E represents the energy of a photon, h is Planck's constant, and f is the frequency of the electromagnetic wave.
Regardless of the frequency of the electromagnetic wave, the energy of each photon is determined by the value of Planck's constant. However, it's important to note that at very low frequencies or long wavelengths, the energy of individual photons may be extremely small compared to higher frequency waves. This is because the energy of a photon is directly proportional to its frequency, so low-frequency waves carry less energy per photon than high-frequency waves.