Properties of Light
Light is energy we can see and it travels in lightwaves.
It is a type of electromagnetic radiation that is visible to the human eye. It is made up of tiny packets of energy called photons and travels through space at the speed of light, which is about 300,000 kilometers per second (186,282 miles per second). Here are some properties of light that are important to understand:
- Reflection: When light hits a surface, it can be reflected off of that surface. The angle at which the wave hits the surface (called the angle of incidence) and the angle at which it is reflected (called the angle of reflection) are related according to the law of reflection.
- Absorption: When light hits a surface, it can also be absorbed by the surface. Different materials absorb different wavelengths to different degrees, which is why some materials appear in different colors.
- Refraction: When light passes through a medium with a different refractive index (such as air to water), it changes direction. This is called refraction. The amount of refraction depends on the angle of incidence and the refractive indices of the two media.
Check out the aligning comic illustrating these properties HERE!
Light and Stars
The Sun is a star that is located at the center of the solar system and is the primary source of light and heat for Earth. It is a medium-sized star compared to other stars in the universe, but it is still much larger and more massive than Earth.
The Sun is a glowing ball of gas that is held together by its own gravity. It is made up mostly of hydrogen and helium, with smaller amounts of other elements. It produces energy through a process called nuclear fusion, in which hydrogen atoms are combined to form helium in the Sun’s core. This process releases a tremendous amount of energy in the form of light and heat, which is what makes the Sun shine.
There are billions of other stars in the Milky Way galaxy alone, and many more in other galaxies. Like the Sun, other stars are glowing balls of gas that produce energy through nuclear fusion. However, stars can vary greatly in size, mass, temperature, and other characteristics. Some are much larger and more massive than the Sun, while others are smaller and less massive. Some are very hot and bright, while others are cooler and dimmer.
Despite their differences, all stars have some things in common. They all produce light and heat through nuclear fusion, and they all are held together by their own gravity. They also all orbit around the center of their galaxies, just like the Sun orbits around the center of the Milky Way.
What is a Light Year?
Light-years are a unit of distance that is used to measure astronomical distances. One light-year is equal to the distance that light can travel in one year, which is about 9.46 trillion kilometers (5.88 trillion miles). Light travels at a constant speed of about 300,000 kilometers per second (186,282 miles per second) in a vacuum, so it takes about a year for light to travel a distance of one light-year.
Light-years are used to express distances to objects in space because these distances are typically much too large to be measured in kilometers or miles. For example, the nearest star to the Sun (besides the Sun itself) is the star Proxima Centauri, which is about 4.2 light-years away. This means that it takes light about 4.2 years to travel from Proxima Centauri to Earth.
Astronomers use light-years to express the distances to objects in the universe because light is the fastest thing that we know of and is used as a reference point for measuring large distances. It is important to note that light-years are a unit of distance, not a unit of time. When we say that an object is “X light-years away,” we are talking about how far away it is, not how long it takes to get there.
Betelgeuse
Betelgeuse is a red supergiant star located in the constellation Orion. It is one of the brightest stars in the night sky and is known for its reddish color and large size.
In terms of distance, Betelgeuse is about 640 light-years away from Earth. This means that it takes light approximately 640 years to travel from Betelgeuse to Earth. Light-years are a unit of distance that is used to measure astronomical distances. One light-year is equal to the distance that light can travel in one year, which is about 9.46 trillion kilometers (5.88 trillion miles).
In late 2019, there were reports that Betelgeuse had suddenly dimmed by about 20% over a period of several months, leading some to speculate that the star might be about to go supernova. However, subsequent observations and analysis showed that the dimming was likely due to a combination of factors, including dust clouds and the star’s natural variability, rather than an imminent explosion.
It is worth noting that even if Betelgeuse were to go supernova, it would not pose a threat to Earth. The star is located about 640 light-years away, which is much too far for the explosion to have any direct effect on our planet. The light from the explosion would take 640 years to reach Earth, and by that time, any harmful radiation would have dissipated.
While it is not clear when or if Betelgeuse will go supernova, it is an interesting and much-studied star that continues to fascinate astronomers and the general public alike.
The Inspiration
In 2013, I was captivated by astronomy and the immense distances and sizes beyond our tiny planet. I was teaching middle school science and creating lesson plans to align with the NGSS standards.
While the science standards did not specifically site Betelgeuse or of lightyears (for Example NGSS Grade 5: Earth’s Place in the Universe and NGSS MS.Waves and Electromagnetic Radiation) igniting curiosity and excitement about this star creates an incentive for students to understand how it all works.
One cannot truly understand how amazing these space distances are without an understanding of the properties of light and how it travels.
I was so fascinated by this star, I felt inspired to teach my students all about it. This was early on in my comic-creating journey, and I had yet to even use rulers and color to clean up the products. At the time, my science comics were simply quick doodles haphazardly thrown onto a piece of paper.
This is one of my first comics, and it is clear they have evolved over time. Initially, my comic series was called The Cool School Rap with the idea that I would write raps to align with each comic. That concept fell through and the actual comics thrived.
While this comic is definitely vintage, it marks the start of my journey to this point. Now I am creating complete lesson plans, a newsletter, YouTube shorts, and posting on social media all with the goal of spreading my passion for science. My ultimate goal is to improve science literacy through my utilization of these visual learning tools.
Lesson Plan Idea
Here is a lesson plan on the properties of light that is suitable for middle school students:
Lesson Objective: Students will understand the properties of light and be able to explain how light travels, reflects, refracts, and absorbs.
Materials needed:
- Whiteboard or blackboard
- Markers or chalk
- Handouts with definitions of key terms (wavelength, frequency, reflection, refraction, absorption)
- Examples of materials that reflect, refract, and absorb light (mirror, prism, colored paper)
- Flashlight or lamp
Lesson Procedure:
- Introduce the topic of light and its properties. Write the key terms on the board and have students copy them into their notebooks.
- Define each term and give examples. Use the handouts and examples to help illustrate the concepts.
- Have students work in pairs to complete a chart that lists the properties of light and provides examples of each.
- Have students use the flashlight or lamp to demonstrate the properties of light. For example, they can shine the light on different surfaces to show reflection, pass the light through a prism to show refraction, and shine the light on different colors of paper to show absorption.
- Have students share their findings with the class and discuss any questions or observations they have.
- As a class, review the key points of the lesson and have students write a summary of what they learned.
Assessment:
- Participation in class discussions and activities
- Completion of the chart on the properties of light
- Written summary of what was learned
Extension:
- Have students research and present on a specific property of light in more detail (such as polarization or the electromagnetic spectrum)
- Have students conduct experiments to demonstrate the properties of light using different materials and techniques
What Color has the Shortest Wavelength?
While I did not touch on this in any of my videos, there are a few questions often asked. Which color has the shortest wavelength? What color has the longest wavelength?
The wavelength of light is related to its color. Shorter wavelengths correspond to blue and violet light and longer wavelengths correspond to red and orange light. This relationship is described by the visible spectrum. This is the range of wavelengths of light that are visible to the human eye. The visible spectrum is often depicted as a rainbow, with the shortest wavelength color on the violet end. The longest wavelength color is on the red end.
What color has the shortest wavelength? Violet
What color has the longest wavelength? Red
The colors of the visible spectrum, from shortest to longest wavelength, are Violet, Indigo, Blue, Green, Yellow, Orange, and Red.
Light of different wavelengths can also be described in terms of its frequency. Frequency is the number of waves that pass a point in a given amount of time. Higher-frequency light corresponds to higher energy photons and shorter wavelengths. Lower-frequency light corresponds to lower energy photons and longer wavelengths.
It is worth noting that the visible spectrum is just a small part of the electromagnetic spectrum, which is the range of all types of electromagnetic radiation. The electromagnetic spectrum includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. All of these have different properties and uses.
