Electromagnetic Spectrum (Simplified): Study with Video Lessons, Practice Problems & Examples

The electromagnetic spectrum encompasses all electromagnetic radiation, ranging from long radio waves to gamma rays. As one moves from left to right, wavelengths decrease while frequencies and energy increase. The visible light spectrum, a small segment of this continuum, includes colors represented by ROYGBIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet), spanning from approximately 700 nm (red) to 380 nm (violet). Understanding this spectrum is crucial for grasping concepts in physics and chemistry, including the behavior of photons and their interactions with matter.

Electromagnetic Spectrum (Simplified) Concept 1

Hey everyone. So in this video, we're going to talk about the electromagnetic spectrum. Now, the electromagnetic spectrum itself is just a continuum of electromagnetic radiation that contains all wavelengths and frequencies. Now, electromagnetic radiation this is just the flow of light energy that itself is traveling at the speed of light through space as either an electric or magnetic field. Now, it was the physicists Max Planck and Albert Einstein that theorized this radiation was made of packets or particles. Now this light particle or packet was referred to as a photon and a group of them was called a quantum. Now as we move through the electromagnetic spectrum, as we go from left to right, we're going to be going from the radio waves all the way to gamma rays. But what we need to realize here is that moving in this direction has a profound effect on our wavelength, our frequency, and also energy. So as you're moving from left to right towards gamma rays, we're going to say that our wavelengths will be decreasing and our frequencies will be increasing. Now remember we talked about this in previous videos that there is a direct relationship between frequency and energy. So here if my frequencies are increasing, that means my energies are also increasing. If we take a look here at the electromagnetic spectrum itself, up here we have µ, which represents Hertz, which represents our frequency. And we're going to start out with our long radio waves. They have energies that are around 100 Hertz or 1 Hertz, and they can go up further as we move from left to right. On the bottom, we have λ as our symbol, which represents wavelength traditionally in meters. So if we're taking a look here, we can see that our frequency here is 1 Hertz and our wavelength is 108 meters. So you can see wavelength is pretty huge. It's a large number, frequency is a very small number. And we're going to start out with our long radio waves to start. When we go past the long radio waves, we're going to go into our radio waves. And remember radio waves themselves are broken up into AM and FM. If you're looking at the dial on your car for the radio, you know that you can transition from AM stations to FM stations. And remember that AM stations typically have smaller numbers, that's because they have smaller frequencies. FM have larger numbers usually in terms of megahertz, and that's why they're higher up. Once we pass radio waves we go into microwave, and then after microwave we go into infrared. Now this portion here that's very colorful, remember this is the portion of the electromagnetic spectrum that we can see with our own eyes without the use of instruments. This is the visible light region. Okay. So you can see that the visible light region makes up a very small portion of the entire electromagnetic spectrum. After the visible light spectrum we go into UV, and after UV we have x-rays and then finally gamma rays. Now, some books may talk about cosmic rays out in space, but we typically don't talk about this within chemistry, so just realize that we're going to go just to gamma rays. Now what can we see here? Well, this wave here represents the relationship of wavelength and frequency. We can see that initially the distance between each wave is pretty big, there's a vast distance between them. Remember that distance represents our wavelength. You can see wavelength starts off pretty high. And what happens as we move from left to right? You can see the wavelength is becoming more tightly packed. That's because my wavelength, the distance between crests of the waves, is decreasing, and the frequency of waves I get per amount of time is increasing, so my frequency is increasing. But you might say, Jules, there are so many different terms here with the electromagnetic spectrum. How am I supposed to remember all of them? Well, that's when we use our memory tool. So our memory tool here says that large rude Martians invented very unusual x-ray guns. So if we take a look here at everything we highlighted we can say large stands for long radio waves, rude stands for radio waves, Martians are microwaves, invented is for infrared, very is for our visible light spectrum, the small portion here, Unusual is for UV. X-ray is for x-rays. And then guns here is for gamma rays. So use this memory tool to help you remember the order of the electromagnetic spectrum. And remember, as we move from long radio waves all the way to gamma rays, we see that our wavelengths are decreasing as our frequency is increasing.

Electromagnetic Spectrum (Simplified) Example 1

So here we're going to use our memory tool to help us with this example question. It says, which kind of electromagnetic radiation contains the greatest amount of energy per atom? Here, remember, as we move from left to right, we're going to say that our frequency increases. So μ is increasing. And this is important to know because remember, energy and frequency are directly related. So, the greatest amount of energy would correlate to the highest frequency. So, who's most to the right here? If we look, microwave is for Martians, so that's out. X-ray is over here, and the only thing higher than that is gamma rays, and we don't have gamma rays listed as an option. So here, our answer would have to be choice b. Remember, "Large rude Martians invented very unusual x-ray guns," stands for long radio waves, radio waves, here we have microwaves, here we have infrared, the visible light spectrum, we have UV light, x-ray and then gamma ray.

Electromagnetic Spectrum (Simplified) Concept 2

So the visible light spectrum represents a small portion of the continuum, the electromagnetic spectrum itself, that can be seen without the aid of instruments by us. And here we're going to say that in order to remember the colors involved with the visible light spectrum, just remember ROY G BIV. Here, R is red, then we have orange, yellow. We have here green, blue, indigo, and violet. Now realize that sometimes in more modern visible light spectrums, they'll combine indigo and violet together and just say it's violet. And when we're talking about the visible light spectrum, realize that it ranges from 700 nanometers for red light all the way to around 380 nanometers for violet light. And remember, in terms of the electromagnetic spectrum, we're going to say that red is near infrared and then the violet end is next to ultraviolet. Now that's blue, but you get what I mean. So that's a good way of remembering what other electromagnetic radiations are near the visible light spectrum. Red is next to the infrared and then violet is next to the ultraviolet. So just remember, the visible light spectrum is important to us because that's what we can see with our bare eyes without the use of any types of instruments.

Which of the following sources of electromagnetic radiation will have the highest energy?

• A. Light A (595 nm)
• B. Light B (0.0303 cm)
• C. Light C (0.000510 m)
• D. Light D (291 μm)

A carbon–oxygen double bond within a sugar molecule absorbs electromagnetic radiation at a frequency of 6.0 x 10¹² s^-1. What portion of the electromagnetic spectrum does this represent?

• A. Radio Waves
• B. Micowave
• C. Infrared
• D. Green Light
• E. Gamma Ray

X-Ray detectors are devices that use scintillators to convert X-rays into light in order to detect X-Rays indirectly. Which of the following would be picked up by an X-Ray detector:radiation with a wavelength of 0.85 nm or a frequency of 6.52 x 10¹¹ s^-1?

• A. radiation with a wavelength of 0.85 nm
• B. radiation with a frequency of 6.52 x 10¹¹ s^-1

Here’s what students ask on this topic:

What is the electromagnetic spectrum and why is it important?

The electromagnetic spectrum is a continuum of all electromagnetic radiation, ranging from long radio waves to gamma rays. It encompasses all wavelengths and frequencies of electromagnetic radiation. Understanding the electromagnetic spectrum is crucial because it helps us comprehend how different types of radiation interact with matter. This knowledge is essential in various fields, including physics, chemistry, and engineering, as it explains phenomena such as the behavior of photons, energy transfer, and the properties of different types of radiation. Additionally, it has practical applications in communication technologies, medical imaging, and even in understanding astronomical observations.

What is the relationship between wavelength, frequency, and energy in the electromagnetic spectrum?

In the electromagnetic spectrum, there is an inverse relationship between wavelength and frequency, and a direct relationship between frequency and energy. As you move from left to right across the spectrum (from long radio waves to gamma rays), the wavelength decreases while the frequency and energy increase. Mathematically, this relationship is expressed as:

$c=\lambda \nu$

where c is the speed of light, λ is the wavelength, and ν is the frequency. Additionally, the energy of a photon is given by:

$E=h\nu$

where E is the energy, and h is Planck's constant. Thus, higher frequency radiation has higher energy and shorter wavelengths.

What is the visible light spectrum and how is it represented?

The visible light spectrum is a small portion of the electromagnetic spectrum that can be seen by the human eye without the aid of instruments. It ranges from approximately 700 nanometers (nm) for red light to 380 nm for violet light. The colors in the visible light spectrum are often remembered using the acronym ROYGBIV, which stands for Red, Orange, Yellow, Green, Blue, Indigo, and Violet. Red light is near the infrared region, while violet light is near the ultraviolet region. This spectrum is important because it represents the range of wavelengths that our eyes can detect, allowing us to perceive the world in color.

How do radio waves differ from gamma rays in the electromagnetic spectrum?

Radio waves and gamma rays are at opposite ends of the electromagnetic spectrum and differ significantly in their properties. Radio waves have the longest wavelengths (ranging from about 1 millimeter to 100 kilometers) and the lowest frequencies (from about 3 kHz to 300 GHz). They are used primarily for communication, such as broadcasting and wireless networks. Gamma rays, on the other hand, have the shortest wavelengths (less than 0.01 nanometers) and the highest frequencies (above 10¹⁹ Hz). They carry the most energy and are produced by nuclear reactions and certain types of radioactive decay. Gamma rays are used in medical imaging and cancer treatment but can be harmful due to their high energy.

What mnemonic can help remember the order of the electromagnetic spectrum?

A useful mnemonic to remember the order of the electromagnetic spectrum is: 'Large Rude Martians Invented Very Unusual X-ray Guns.' This stands for Long radio waves, Radio waves, Microwaves, Infrared, Visible light, Ultraviolet, X-rays, and Gamma rays. This mnemonic helps recall the sequence from the longest wavelengths and lowest frequencies (long radio waves) to the shortest wavelengths and highest frequencies (gamma rays). Using such memory tools can make it easier to remember the order and properties of different types of electromagnetic radiation.