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What are the characteristics of the electromagnetic spectrum and how does light fit into the spectrum?

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Recall that light is a form of electromagnetic radiation. Electromagnetic radiation is the transfer of energy by electromagnetic waves.

In general, a wave starts from a vibrating source. The source of electromagnetic waves is an electron that is vibrating between the electric and the magnetic fields. Electromagnetic waves are created when the electron is accelerated by an electric field. This acceleration causes the electron to move, and it produces oscillating (changing) electric and magnetic fields that are at right angles to each other.

An electromagnetic wave: Enter key opens full-screen view with caption; escape key exits full screen.
An electromagnetic wave consisting of electric and magnetic oscillating fields.

The electromagnetic spectrum is the full range of electromagnetic radiation. In the electromagnetic spectrum, the forms of electromagnetic radiation are categorized by a range of the amount of energy they carry, noted by their wavelengths and frequency.

The different types of electromagnetic waves are shown in this image of the electromagnetic spectrum. The image shows the types of electromagnetic waves with the lowest energy (longest wavelength and lowest frequency) on the left and the highest energy waves (shortest wavelength and highest frequency) on the right.

Notice that visible light is a small part of the electromagnetic spectrum. Also notice that in the visible-light part of the spectrum, the different wavelengths produce different colors.

Electro magnetic spectrum: Enter key opens full-screen view with caption; escape key exits full screen.
Electro magnetic spectrum

Diagram of the seven categories of electromagnetic radiation in order from longest wavelength to shortest wavelength. The categories from left to right are labelled radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays. The visible light category is divided up to show the colors red, orange, yellow, green, blue, and purple.

The Speed of Light

Electromagnetic waves can travel through a vacuum, which is how the light and heat from the sun reach the Earth. The speed of light in a vacuum is 3.0 x 108 meters per second.

\(c = \lambda\nu\)

Question

The product of the frequency and the wavelength of a particular type of wave in a given medium is constant. Since electromagnetic waves have the same speed in a vacuum, the wavelength and the frequency are inversely related. This means that as one goes up, the other goes down. Since they are inversely related, what happens to the frequency of a wave as a wavelength gets longer?

As a wavelength gets longer, the frequency decreases.

Reflection

Explain how light is related to the electromagnetic spectrum.

Explain how the different colors of light provide evidence for light behaving as a wave and not a particle.