# Light as a Corpuscle: Exploring Planck's Theory

• Bashyboy
In summary: It is not meant to be taken literally but people do!In summary, Planck's equation ##E = h \nu## describes the energy of light as a collection of fixed entities, or quanta. The use of the term "corpuscular" in this context is not accurate, and the concept of a photon as a particle can be misleading.
Bashyboy
I am reading Schiff's book on Quantum Mechanics.He is discussing how Planck sought to account for the Blackbody radiation phenomenon, and correctly did so by assuming that the energy of light was described by the equation ##E = h \nu##. He then claims that, because the energy of light is described by this equation, light is "sometimes like a stream of corpuscular quanta."

I am having difficulty seeing how ##E = h \nu## describing the energy of light implies that it is a particle. Couldn't light till be a wave and have its energy described by ##E = h \nu##?

Bashyboy said:
I am having difficulty seeing how ##E = h \nu## describing the energy of light implies that it is a particle. Couldn't light till be a wave and have its energy described by ##E = h \nu##?

If the light is very intense then the energy delivered by the light per unit time is large; and if the light is dim then the energy delivered per unit time is small. However, the frequency and the wavelength of the light is the same in both cases, so the formula ##E=h\nu## yields the same constant value for ##E## in both cases.

Thus, Planck's hypothesis was that ##E## is the amount of energy delivered by a single corpuscle, and when a bright light is delivering a large amount of energy per unit time, that should be interpreted as a large number of corpuscles each with energy ##E## being delivered.

Bashyboy said:
I am reading Schiff's book on Quantum Mechanics.He is discussing how Planck sought to account for the Blackbody radiation phenomenon, and correctly did so by assuming that the energy of light was described by the equation ##E = h \nu##. He then claims that, because the energy of light is described by this equation, light is "sometimes like a stream of corpuscular quanta."

I am having difficulty seeing how ##E = h \nu## describing the energy of light implies that it is a particle. Couldn't light till be a wave and have its energy described by ##E = h \nu##?
Somewhat yes. The point is that light is here described as consisting of a collection of entities with fixed energy. IMHO, "corpuscular" doesn't follow from that equation (what does follow from it is "quanta").

The word "corpuscle" has fallen out of use because it doesn't imply the right properties for the packets of energy in which EM radiation is delivered (the photon). I blame dear old Richard Feinman for his insistence that the Photon 'is' a particle because it has caused so many beginners to hare off in an unhelpful direction in their studies. He understood what he meant but most people don't seem to. The particle he meant was not a 'little bullet' but people insist on viewing photons that way. It is not helped by the Feinman Diagram - which is purely symbolic - and which shows the photon as a wiggly line. drawn from place to place.

vanhees71

## 1. What is Planck's theory?

Planck's theory, also known as Planck's constant, is a fundamental concept in quantum mechanics that describes the relationship between the energy of a photon and its frequency. It states that the energy of a photon is directly proportional to its frequency, with Planck's constant serving as the proportionality constant.

## 2. How does Planck's theory explain light as a corpuscle?

Planck's theory explains light as a corpuscle, or a particle, by proposing that light is made up of discrete packets of energy called photons. These photons behave like particles, with a specific energy and frequency, rather than waves. This theory helped to reconcile the wave-particle duality of light.

## 3. What evidence supports Planck's theory?

There is a significant amount of evidence that supports Planck's theory. One key piece of evidence is the photoelectric effect, where electrons are emitted from a metal surface when light of a certain frequency is shone on it. This phenomenon can only be explained by the particle nature of light, as predicted by Planck's theory.

## 4. How does Planck's theory impact our understanding of the universe?

Planck's theory has had a major impact on our understanding of the universe, particularly in the field of quantum mechanics. It has helped to explain the behavior of subatomic particles and has led to groundbreaking discoveries, such as the development of the theory of relativity and the concept of wave-particle duality.

## 5. Can Planck's theory be applied to other forms of energy?

Yes, Planck's theory can be applied to other forms of energy besides light. It can be used to explain the behavior of other particles, such as electrons, and has also been applied to other fields of study, including chemistry and thermodynamics. Planck's theory has been essential in advancing our understanding of the fundamental building blocks of the universe.

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