Increasing intensity causes a contradiction in classical physics?

However, the photoelectric effect shows that increasing the intensity of light does not increase the kinetic energy of photoelectrons, but rather increases the number of electrons emitted. This contradicts classical physics and led to the development of quantum mechanics. The change in color of the light, on the other hand, does increase the kinetic energy of the emitted photoelectrons. This phenomenon has been extensively studied in the famous photoelectric effect, which has helped shape our understanding of quantum mechanics. In summary, the photoelectric effect shows a contradiction between classical physics and quantum mechanics, as increasing the intensity of light does not increase the kinetic energy of photoelectrons, but changing the color of the light does.
  • #1
Turion
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According to my prof, increasing intensity of the light source in a photocell for the photoelectric effect does not increase the kinetic energy of photoelectrons emitted. Instead, the number of electrons emitted (and current) increases. Changing the colour of the light causes an increase in kinetic energy of the photoelectrons emitted.

Why is this a contradiction in classical physics as my prof claims?
 
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  • #3
Classical physics states that the intensity of light should be proportional to the square of the amplitude of the wave and should have nothing to do with its frequency.
 

Related to Increasing intensity causes a contradiction in classical physics?

1. What do you mean by "intensity" in classical physics?

In classical physics, intensity refers to the amount of energy that is transferred through a given area in a given amount of time. It is often used to describe the strength or magnitude of a physical phenomenon, such as the brightness of light or the loudness of sound.

2. How does increasing intensity lead to a contradiction in classical physics?

In classical physics, it is assumed that the relationship between intensity and a physical phenomenon is linear. This means that as intensity increases, the observed effect should also increase in a predictable manner. However, in certain cases, increasing intensity can lead to unexpected or contradictory results that cannot be explained by classical physics principles.

3. Can you provide an example of how increasing intensity causes a contradiction in classical physics?

One example is the photoelectric effect, where increasing the intensity of light shone on a metal surface does not result in an increase in the number of electrons emitted, as classical physics would predict. Instead, the maximum energy of the emitted electrons increases, while the number of electrons stays constant. This contradicts the classical physics principle that the energy of emitted electrons should increase with increasing intensity.

4. How is this contradiction explained in modern physics?

The photoelectric effect, and other similar contradictions, can be explained by the principles of quantum mechanics. In quantum mechanics, the relationship between intensity and physical phenomena is not linear, and instead, the energy of particles is quantized. This means that increasing the intensity of a physical phenomenon can lead to the emission of higher-energy particles, rather than an increase in the number of particles.

5. Are there any other instances where increasing intensity causes a contradiction in classical physics?

Yes, another example is the ultraviolet catastrophe, where classical physics predicts that the intensity of blackbody radiation should increase infinitely as the frequency of the radiation increases. However, this is not observed in reality, and the intensity instead reaches a maximum value and then decreases. This contradiction was explained by Max Planck's introduction of the quantum theory of radiation.

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