Intensity of Light using Quantum theory

In summary, the conversation discusses the reflection of light at a glass-air boundary and how quantum theory predicts a 4% chance of reflection for a single photon, which differs from the classical prediction of 8% reflection for a light beam. The behavior of the photon is described by a wave function, and it is not completely unpredictable but follows a probabilistic behavior.
  • #1
Seven of Nine
1
0

Homework Statement


Approximately 4% of the intensity of light is reflected at a glass-air boundary. Classically one expects roughly 8% of light to be reflected from a thin glass plate (4% at the front and back boundary). Outline briefly what quantum theory predicts for a single photon instead of a light beam, in particular, say how this differs from the classical prediction.

2. The attempt at a solution
If light shines on an imperfectly transparent sheet of glass it may happen that 96% of light transfers through the glass, this makes sense if light were a wave, as the wave splits and a smaller wave is reflected back. But light is considered as a steam of particles so the glass has a 96% chance of being transmitted and 4% chance of being reflected. The behaviour of the photon is totally random and unpredictable. It is defined as a wave function. A particle when not being measured or located takes the form of a field of probable locations some being more probable or as likely than others.

Is that right?
 
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  • #2
Your answer is not wrong but it is not clear.
They are demanding the behavior of a single photon. So I would advise to clean up this part:
Seven of Nine said:
If light shines on an imperfectly transparent sheet of glass it may happen that 96% of light transfers through the glass, this makes sense if light were a wave, as the wave splits and a smaller wave is reflected back. But light is considered as a steam of particles so the glass has a 96% chance of being transmitted and 4% chance of being reflected.
I couldn't quite get what you wanted to say.

Then I would skip that part:
Seven of Nine said:
The behaviour of the photon is totally random and unpredictable.
since it is not correct. It is true that the behavior follows a probabilistic behavior, but that does not mean that it is "totally unpredictable". However, saying that It is described by a wavefunction suffices. And the last sentence is also good.

When you correct the first part maybe move it after the second one. You would then have explained the general quantum behavior and moved on to the specific problem.
 

1. What is quantum theory and how does it relate to the intensity of light?

Quantum theory is a scientific theory that explains the behavior of matter and energy on a very small scale, such as atoms and subatomic particles. It relates to the intensity of light because it explains how light is made up of tiny packets of energy called photons, and how the intensity of light is determined by the number of photons present.

2. How is the intensity of light measured using quantum theory?

The intensity of light is measured using a unit called the photon flux, which is the number of photons per unit area per unit time. This can be measured using specialized equipment such as a photometer or a spectrometer.

3. Can the intensity of light be changed by altering the energy of individual photons?

Yes, the intensity of light can be changed by increasing or decreasing the energy of individual photons. This can be done by using devices such as filters or polarizers, which can alter the energy and direction of photons.

4. What is the relationship between the intensity of light and the frequency of photons?

The intensity of light is directly proportional to the frequency of photons. This means that as the frequency of photons increases, the intensity of light also increases.

5. Can the intensity of light be described using classical physics instead of quantum theory?

No, the intensity of light cannot be fully described using classical physics. Classical physics treats light as a continuous wave, whereas quantum theory shows that light is made up of discrete particles with specific energies. The intensity of light can only be fully explained using quantum theory.

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