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Photons are teeny-tiny particles that don't weigh anything, so they're called "massless." help carry energy around as electromagnetic waves. Whenever a particle releases energy, photons show up! There are lots of things that can make photons appear, like when unstable isotopes break down and emit radioactivity.

Photon properties

Photons are super speedy particles that travel at nearly 300,000,000m/s through the vacuum of space. They come in different wavelengths, which determine how much energy they have. Gamma rays have shorter wavelengths and more energy, while radio waves have longer wavelengths and less energy.

Even though they're full of energy, photons don't have any mass at all. They're a special kind of pure energy that doesn't come from other particles. But here's a strange fact - photons don't react to gravity forces unless they're in something really massive, like a black hole.

The sunlight is made of photons. In a rainbow, we see the decomposition of light in photons with different wavelengths
The sunlight is made of photons. In a rainbow, we see the decomposition of light in photons with different wavelengths

The energy of a photon

The energy of a photon depends on its wavelength. Shorter wavelengths have higher energy as they oscillate faster, while larger wavelengths, which oscillate more slowly, have lower energy. To obtain the photon energy, you need to multiply the velocity of the light ‘c’ in the vacuum by the Planck constant ‘h’ and divide this by the wavelength of the photon ‘λ’. The formula to obtain the photon energy is:

E = h · c0 / λ

The Planck constant is equal to 6.63 ⋅ 10 ^ -34 J ⋅ s, and the light velocity in the vacuum is close to 3 ⋅ 10 ^ 8 m/s.

Energy wavelength dependence

The wavelength-energy relationship holds true for all forms of electromagnetic energy. By measuring the wavelength of a photon, we can learn about some of its characteristics. Comparing the energy of different wavelengths allows us to understand how the wavelength affects a photon's energy.

For example, the energy of radio waves used in radio transmissions can be calculated by first determining the wavelength using the relationship between wavelength and frequency. The energy can then be calculated using the photon energy equation. The energy of radio waves is relatively low due to their long wavelengths.

In contrast, visible light, such as the yellow color, has a much higher energy due to its shorter wavelength. The energy can be calculated using the energy-photon relationship. While still small compared to everyday things, it is much larger than the energy of radio waves.

X-rays used in medical imaging have an even higher energy due to their much shorter wavelength. The energy can be calculated using the same equations. The energy from x-rays is much larger than that of visible light.

In summary, the wavelength of a photon is directly related to its energy, and calculating the energy of different wavelengths can help us understand the characteristics of electromagnetic energy.

Approximate spectrum of energy vs wavelength for any photon
Figure 2. Approximate spectrum of energy vs wavelength for any photon

Light velocity

It is important to note that the velocity of light is not constant and varies depending on the medium in which it travels. While light travels at a speed of approximately 300,000,000 m/s in a vacuum, it travels slower in other materials, such as the atmosphere or solid materials like diamonds.

Despite having no mass, photons are responsible for carrying energy in the form of electromagnetic waves. Visible light, such as sunlight, consists of photons. The energy of a photon is directly related to its wavelength, with shorter wavelengths having higher energy and longer wavelengths having lower energy.

Photons are the fastest particles in the known universe, traveling at the speed of light in a vacuum. This speed is approximately 300,000,000 m/s. Understanding the properties and behavior of photons is essential in many fields, physics, chemistry, and engineering.


What is a photon?

A photon is a particle that is responsible for exchanging energy and carry the electromagnetic force.

What are photons made of?

Photons are basic particles that are not made of any other particle.

How are photons measured?

Photons have one quantity that can be measured. This is their wavelength, which also defines their energy. To measure the wavelength, you need electronic sensors that can detect the photon’s frequency. The wavelength is equal to the velocity of light divided by the photon’s frequency, i.e.:f = c/λ

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