# A question about the light spectrum

• sangho
In summary, the electromagnetic spectrum is a continuous spectrum with all wavelengths possible due to various sources of electromagnetic radiation. The emission of radiation from excited atoms, scattering of photons, and other phenomena contribute to the diversity of wavelengths in the spectrum. However, there may be limitations at both the high and low ends of the spectrum due to energy constraints and measurement capabilities.
sangho
For any given number(length), say L, is always there an electromagnetic wave with the wavelength L ?

As I know, the source of electromagnetic wave is the energy emission of electrons changing it's quantum state in an atom.
But there are at most about 120 atoms there, and the quantum numbers are, mathematically saying, countable. So I think the electromagnetic spectrum is not filled with all numbers in the axis.

The E-M spectrum is a continuous spectrum, and all wavelengths are possible. There are many reasons why. In the case of emission of radiation by an excited atom, since the emission of the radiation must conserve energy and momentum, the wavelength of the light emitted depends on the state of motion of the atom. Also, after a photon is emitted from an atom, the photon can scatter off of something, like a free electron, which changes its wavelength. There are also many other sources of EM radiation besides the de-excitation of an excited atom. For example, an electron scattering off a nucleus can emit radiation through bremsstrahlung. Since the electron and nucleus can have any state of motion and meet at any angle, this results in a continuous spectrum.

At the very high end of the spectrum, there may not be enough energy to feasibly create an EM wave of the requisite wavelength or to survive its detection.. Though, if one is given freedom to choose one's frame of reference, then a particular EM wave can have any wavelength one chooses.

At the very low end of the spectrum, the wave may be longer than is feasible to create, detect or measure.

There's also the issue of doppler shift and cosmological redshift, which are both continuous in nature.

## 1. What is the light spectrum?

The light spectrum refers to the range of electromagnetic radiation that is visible to the human eye. It includes all the colors of the rainbow, from red to violet, and also includes non-visible forms of light such as infrared and ultraviolet.

## 2. How is the light spectrum produced?

The light spectrum is produced when an object absorbs and reflects different wavelengths of light. For example, a red apple appears red because it absorbs all wavelengths of light except for red, which it reflects. The combination of all the reflected wavelengths creates the color that we see.

## 3. Why is the light spectrum important?

The light spectrum is important because it allows us to see and perceive the world around us. It also plays a crucial role in many scientific fields, such as astronomy, chemistry, and biology. Understanding the light spectrum can help us gather information about the composition and properties of objects and substances.

## 4. How is the light spectrum measured?

The light spectrum is measured using a device called a spectrometer. This instrument separates light into its different wavelengths and measures the intensity of each wavelength. The data collected by a spectrometer can be used to create a visual representation of the light spectrum, known as a spectrum graph.

## 5. Can the light spectrum be seen with the naked eye?

Yes, the light spectrum can be seen with the naked eye. However, our eyes are only able to see a small portion of the entire spectrum, known as the visible light spectrum. Other forms of light, such as radio waves and gamma rays, cannot be seen without the use of specialized equipment.

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