Amplitude of Electromagnetic wave?

Click For Summary
SUMMARY

The energy of an electromagnetic wave is determined by its frequency, as expressed in the equation E = hf, where E is energy, h is Planck's constant, and f is frequency. This principle was established through the photoelectric effect, which demonstrated that electrons are ejected from a metal only when the light frequency exceeds a certain threshold, regardless of light intensity. While amplitude does not directly affect the energy of a single photon, it correlates with the number of photons present, thereby influencing the overall intensity of the wave.

PREREQUISITES
  • Understanding of the photoelectric effect
  • Familiarity with Planck's constant (h)
  • Basic knowledge of electromagnetic wave properties
  • Concept of photon energy and intensity
NEXT STEPS
  • Study the photoelectric effect and its implications in quantum mechanics
  • Explore the relationship between amplitude and photon count in electromagnetic waves
  • Learn about Planck's constant and its role in quantum physics
  • Investigate the historical context of energy theories prior to Einstein's contributions
USEFUL FOR

Students of physics, educators teaching quantum mechanics, and researchers interested in the properties of electromagnetic waves and their energy dynamics.

The_Thinker
Messages
145
Reaction score
2
How come the energy of an electromagnetic wave depends only on its frequency?

Given by E = hf.

How come the energy depends only on the frequency of the wave and not on the magnitude of the E component of the wave?

Doesn't the energy depend on the amplitude? Or is there no such thing?
 
Physics news on Phys.org
The_Thinker said:
How come the energy of an electromagnetic wave depends only on its frequency?

It doesn't. It also depends on the amplitude. The equation you wrote was for a single photon.
 
This was found with the photoelectric effect and interpreted by Einstein. It meant that electrons could not be ejected from a metal unless the light was above a certain frequency even if you made the light more "intense." (It used to be thought that energy was proportional to the intensity prior to this point). Changing the frequency of the light and not the intensity of the light caused the electrons to be ejected from the metal. It was later found that the intensity is proportional to the number of photons, not the energy.
 

Similar threads

Undergrad Energy of an electromagnetic wave
  • · Replies 15 ·
Replies
15
Views
3K
Undergrad How to Measure the Energy of an Electromagnetic Wave?
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Mechanism of Energy Conservation in Zero-Amplitude Sum of EM Waveforms
  • · Replies 21 ·
Replies
21
Views
2K
Undergrad What determines if wave components are independent vs coherent?
  • · Replies 3 ·
Replies
3
Views
543
Undergrad Behaviour of EM-wave near a non-resonant antenna
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad Do electromagnetic waves fade with distance in vacuum?
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad Are voltage and current waves in transmission lines an artifice?
  • · Replies 6 ·
Replies
6
Views
2K
Graduate Voltage and current waves in a transmission line
  • · Replies 4 ·
Replies
4
Views
3K
Undergrad How Do Time-Varying Currents in Conductors Generate EM Fields and Waves?
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Energy emitted by EM sources under constructive interference
  • · Replies 7 ·
Replies
7
Views
1K