What’s the difference between energy in an electromagnetic wave and transmit power?

Question

As I understand, Energy of an electromagnetic wave has a direct relationship to frequency. A higher Energy wave is smaller in length at greater frequency. But Transmit Power can be increased without altering the frequency. Transmit Power of a WiFi router can be changed for example; but frequency remains 2.4GHz or 5GHz. Obviously in this example Transmit Power is controlled by a human; energy may or may not be. But what are the fundamental differences between Energy and Transmit Power?

Answer 1

Electromagnetic waves are photons, and the energy of a photon is indeed determined by its frequency $f$ according to $E = h \cdot f$. However, you can simply emit more photons to increase signal strength. In classical physics, more photons would mean an electromagnetic wave of larger amplitude.