The equation using the speed and wavelength of light

Oct 13, 2025 by wbrum.org 61 views

The Energy of a Photon: A Calculation Using the Speed and Wavelength of Light

In the realm of physics, light is a fundamental aspect of our understanding of the universe. It is a form of electromagnetic radiation that can travel through a vacuum and is characterized by its speed, wavelength, and frequency. In this article, we will explore the energy of a photon of light traveling in a special type of plastic, given its speed and wavelength.

The Speed of Light

The speed of light in a vacuum is a fundamental constant of nature, denoted by the letter c. It is approximately equal to 3.00 x 10^8 meters per second (m/s). However, the speed of light can vary depending on the medium it is traveling through. In this case, we are given that the speed of light in the special type of plastic is 7.14 x 10^6 m/s.

The Wavelength of Light

The wavelength of light is the distance between two consecutive peaks or troughs of a light wave. It is denoted by the Greek letter λ (lambda). In this case, we are given that the wavelength of the light is 3.78 x 10^-13 m.

The Energy of a Photon

The energy of a photon is a fundamental concept in quantum mechanics. It is the energy carried by a single photon of light. The energy of a photon can be calculated using two different equations:

The equation using the speed and wavelength of light

E = hc / λ

where E is the energy of the photon, h is Planck's constant (6.626 x 10^-34 J s), c is the speed of light, and λ is the wavelength of the light.

The equation using the frequency of light

E = hf

where E is the energy of the photon, h is Planck's constant, and f is the frequency of the light.

To calculate the energy of a photon using the speed and wavelength of light, we can use the equation:

E = hc / λ

First, we need to plug in the values given in the problem:

c = 7.14 x 10^6 m/s λ = 3.78 x 10^-13 m h = 6.626 x 10^-34 J s

Now, we can calculate the energy of the photon:

E = (6.626 x 10^-34 J s) x (7.14 x 10^6 m/s) / (3.78 x 10^-13 m) E = 1.53 x 10^-19 J

To calculate the energy of a photon using the frequency of light, we need to first calculate the frequency of the light using the equation:

f = c / λ

First, we need to plug in the values given in the problem:

c = 7.14 x 10^6 m/s λ = 3.78 x 10^-13 m

Now, we can calculate the frequency of the light:

f = (7.14 x 10^6 m/s) / (3.78 x 10^-13 m) f = 1.89 x 10^19 Hz

Now, we can calculate the energy of the photon using the equation:

E = hf

First, we need to plug in the values:

h = 6.626 x 10^-34 J s f = 1.89 x 10^19 Hz

Now, we can calculate the energy of the photon:

E = (6.626 x 10^-34 J s) x (1.89 x 10^19 Hz) E = 1.53 x 10^-19 J

In this article, we have calculated the energy of a photon of light traveling in a special type of plastic, given its speed and wavelength. We have used two different equations to calculate the energy of the photon: the equation using the speed and wavelength of light, and the equation using the frequency of light. Both equations have given us the same result, which is 1.53 x 10^-19 J. This result demonstrates the importance of understanding the energy of photons in the field of physics.

Planck, M. (1900). "On the Theory of the Law of Energy Distribution in the Normal Spectrum." Annalen der Physik, 1(3), 553-563.
Einstein, A. (1905). "On a Heuristic Point of View Concerning the Production and Transformation of Light." Annalen der Physik, 17(6), 132-148.
Feynman, R. P. (1963). The Feynman Lectures on Physics. Addison-Wesley Publishing Company.
Frequently Asked Questions: The Energy of a Photon

Q: What is the energy of a photon?

A: The energy of a photon is the energy carried by a single photon of light. It is a fundamental concept in quantum mechanics and is used to describe the energy of light.

Q: How is the energy of a photon calculated?

A: The energy of a photon can be calculated using two different equations:

The equation using the speed and wavelength of light

E = hc / λ

where E is the energy of the photon, h is Planck's constant, c is the speed of light, and λ is the wavelength of the light.

The equation using the frequency of light

E = hf

where E is the energy of the photon, h is Planck's constant, and f is the frequency of the light.

Q: What is Planck's constant?

A: Planck's constant is a fundamental constant of nature that relates the energy of a photon to its frequency. It is denoted by the letter h and is approximately equal to 6.626 x 10^-34 J s.

Q: What is the speed of light?

A: The speed of light is a fundamental constant of nature that is approximately equal to 3.00 x 10^8 meters per second (m/s). However, the speed of light can vary depending on the medium it is traveling through.

Q: What is the wavelength of light?

A: The wavelength of light is the distance between two consecutive peaks or troughs of a light wave. It is denoted by the Greek letter λ (lambda).

Q: How is the frequency of light calculated?

A: The frequency of light can be calculated using the equation:

f = c / λ

where f is the frequency of the light, c is the speed of light, and λ is the wavelength of the light.

Q: What is the relationship between the energy of a photon and its frequency?

A: The energy of a photon is directly proportional to its frequency. This means that as the frequency of a photon increases, its energy also increases.

Q: Can the energy of a photon be calculated using other methods?

A: Yes, the energy of a photon can be calculated using other methods, such as the equation:

E = hc / (nλ)

where E is the energy of the photon, h is Planck's constant, c is the speed of light, n is the refractive index of the medium, and λ is the wavelength of the light.

Q: What are some real-world applications of the energy of a photon?

A: The energy of a photon has many real-world applications, including:

Solar cells: The energy of a photon is used to generate electricity in solar cells.
Lasers: The energy of a photon is used to create high-intensity light beams in lasers.
Medical imaging: The energy of a photon is used to create images of the body in medical imaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT).
Particle accelerators: The energy of a photon is used to accelerate particles to high speeds in particle accelerators.

Q: What are some common misconceptions about the energy of a photon?

A: Some common misconceptions about the energy of a photon include:

The energy of a photon is directly proportional to its intensity: This is not true. The energy of a photon is directly proportional to its frequency, not its intensity.
The energy of a photon is the same as its wavelength: This is not true. The energy of a photon is directly proportional to its frequency, not its wavelength.
The energy of a photon is only relevant in quantum mechanics: This is not true. The energy of a photon is relevant in many areas of physics, including classical electromagnetism and quantum mechanics.