Exploring the Threshold Frequency: Evidence for the Particle Theory of Light

In summary, the photoelectric effect supports the particle theory of light because it demonstrates that the energy required to release electrons from a metal is dependent on the frequency of the incident light, rather than its intensity. This phenomenon cannot be explained using a wave approach to light and led to the development of the photon or particle-like model for light. The photoelectric effect also supports the concept of quantization of electromagnetic radiation and the existence of photons as actual entities, as shown by the Compton effect.
  • #1
Minnie
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Why does the concept of a threshold frequency for metallic surfaces support the particle theory of light? I understand why it conflicts with the wave theory, but why does it support the particle theory??
Any help would be gr8!
Minnie, xoxo.
 
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  • #2
How can you relate frequency to a photon?
 
  • #3
The photoelectric effect is the emission of photoelectrons from a clean metal surface due to incident light whose frequency is greater than a threshold frequency. This phenomenon cannot be explained using a wave apporach to light, and its explanation led to the development of the photon or particle-like model for light.
In considering the photon model, a beam of light consists of a stream of photons, each carrying an energy, E(photon)=hf (h=planck's constant; f=frequency). The total energy in the beam will be Nhf, where N is the number of photons in the beam.
Not entirely sure what you were asking, since light occurs at many different frequencies and wavelengths, according the the equation c=f x wavelength and with changing frequency, there is a change in colour of light, or type of radiation if we move outside the visible spectrum.
Hope this helps!
Minnie, xoxo.
 
  • #4
I think ranger's question was meant to provoke an answer to your original question "why does the photoelectric effect support the particle theory of light?"

The photoelectric effect supports the particle theory of light because it shows that the energy required to release electrons from a metal is totally dependent upon the frequency of the light, and not the intensity. Therefore, certain frequencies of light, no matter how intense, cannot cause an electron to be emitted from the surface of a metal.
 
  • #5
Minnie said:
The photoelectric effect is the emission of photoelectrons from a clean metal surface due to incident light whose frequency is greater than a threshold frequency. This phenomenon cannot be explained using a wave apporach to light
Who said it? Mandl & Wolf - Optical Coherence and Quantum Optics - shows the opposite.
 
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  • #6
lightarrow said:
Who said it? Mandl & Wolf - Optical Coherence and Quantum Optics - shows the opposite.

I couldn't have said it better. A much better statement of the consequence of the photoelectric effect experiment would be to say that the photoelectric effect demonstrates that the world has quantum mechanical properties; but, does not determine whether the most relevant properties are those of light or of matter.
 
  • #7
Well, the particle theory was proposed first, because when light greater than or equal to the threshold frequency was shone on the correponding (to the threshold frequency) surface, even for a weak frequency, which supports the quantisation of electromagnetic radiation, i.e., light, and that for a fixed frequency and retarding potential, the photocurrent was directly proportional to the light intensity (amplitude). The quantisation of EM radiation was supported because throwing lots of little packets of energy each without enough energy to free an electron did not free any electrons but throwing even very little amount of little packets of lots of energy freed some electrons. Secondly, because of this quantisation and the old corpuscular theory, the photon was proposed. The photon was shown to be an actual entity by the Compton effect.
 

What is the particle theory of light?

The particle theory of light, also known as the corpuscular theory, states that light is made up of tiny particles called photons. These particles travel in straight lines and have mass and energy.

Who proposed the particle theory of light?

The particle theory of light was first proposed by Sir Isaac Newton in the 17th century. He believed that light was made up of small particles that were emitted from a light source and traveled in a straight line until they were absorbed or reflected.

How does the particle theory of light explain the behavior of light?

The particle theory of light explains the behavior of light by stating that it travels in straight lines, can be absorbed or reflected, and its energy is dependent on the frequency of the light waves. It also explains phenomena such as refraction and diffraction.

What is the difference between the particle theory and the wave theory of light?

The wave theory of light, also known as the electromagnetic theory, states that light behaves like a wave and does not have mass. It explains phenomena such as interference and polarization. The particle theory, on the other hand, states that light is made up of particles and has mass.

Is the particle theory of light still accepted today?

While the particle theory of light was widely accepted in the 17th and 18th centuries, it was later replaced by the wave theory. However, with the discovery of the photon in the early 20th century, the particle theory was revived and is still accepted today alongside the wave theory as a dual nature of light.

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