|
Abstract Why is it more comfortable to wear light-colored clothes on a hot summer day? Why wear a dark-colored jacket for early-morning fishing on a cold lake? How much difference can it make? Here's a project where you can quantify how much difference color makes for absorbing heat.Objective The goal of this project is to see how the color of an object affects how much heat it absorbs when exposed to incandescent light. Introduction Light is an example of an electromagnetic wave. Electromagnetic waves can travel through the vacuum of interstellar space. They do not depend on an external medium—unlike a mechanical wave such as a sound wave which must travel through air, water, or some solid medium. Electromagnetic waves cover a huge range of frequencies, from high-frequency gamma rays and x-rays, to ultraviolet light, visible light, and infrared light, and on into microwaves and radio waves. As the frequency decreases, so does the energy. The wavelength of an electromagnetic wave is inversely proportional to its frequency. So waves with high frequency have short wavelengths, and waves with low frequency have long wavelengths. Electromagnetic waves interact with materials in different ways, depending on the nature of the material and the frequency of the electromagnetic wave. Light is the range of electromagnetic waves that are visible (Figure 1). For humans, the range of visible wavelengths is from 400 to 700 nm (1 nm = 1 ×10−9 m).
This range of wavelengths is called the visible spectrum of light. When you see a rainbow in the sky, or white light that has been refracted through a prism, or diffracted by the regular surface of a CD, you are seeing a spectrum of colors. The different colors are related to the different wavelengths of light. Violet light is at the short-wavelength end of the visible spectrum (400 nm), and red light is at the long-wavelength end of the visible spectrum (700 nm), with the rainbow of colors in between. We perceive different colors because our visual system has evolved to make use of the spectral information in reflected light. When light interacts with an object, the light can be absorbed by the object, reflected by the object, or transmitted by the object. For example, when you look at yourself in the mirror, the light that you are seeing has been relected by the mirror, transmitted through the air, through your cornea, through the lens of your eye, and through two layers of cells in your retina before it is absorbed by light-sensitive pigments in your photoreceptor cells. The energy from the absorbed light starts a cascade of chemical reactions in your photoreceptors that ultimately leads to your percpeption: seeing yourself in the mirror. Objects in the world have different colors depending on which parts of the visible spectrum they absorb, and which parts of the visible spectrum they reflect. Red objects reflect long wavelengths of light (and absorb shorter wavelengths), while blue objects reflect short wavelengths of light (and absorb longer wavelengths). Black objects absorb all visible wavelengths about equally, and white objects reflect all visible wavelengths about equally. Light that is absorbed by an object is usually converted into heat energy. The goal of this project is to measure how much heat is produced by the absorption of light by different colors. You'll use an incandescent light (a heat lamp), and water-filled jars wrapped with different colors of construction paper. By measuring how much the temperature of the water increases, you'll have a measure of how much light was absorbed by each color. Before you get started, study Figure 2 below and then try to predict what your results will be. The graph compares the spectrum of sunlight with the spectrum of an incandescent bulb. You can see that sunlight has much more energy (brightness) in the range of visible wavelengths (gray shaded region), while the incandescent bulb has more energy in the red and infrared (invisible, longer-wavelength electromagnetic radiation) region of the spectrum.
Terms, Concepts, and Questions to Start Background Research To do this project, you should do research that enables you to understand the following terms and concepts:
Questions
Bibliography
Materials and Equipment To do this experiment you will need the following materials and equipment:
Experimental Procedure
Variations
Credits Andrew Olson, Ph.D., Science Buddies Sources
|
If you like this project, you might enjoy exploring related careers.
![]() |
Physicist Physicists have a big goal in mind—to understand the nature of the entire universe and everything in it! To reach that goal, they observe and measure natural events seen on Earth and in the universe, and then develop theories, using mathematics, to explain why those phenomena occur. Physicists take on the challenge of explaining events that happen on the grandest scale imaginable to those that happen at the level of the smallest atomic particles. Their theories are then applied to human-scale projects to bring people new technologies, like computers, lasers, and fusion energy. |
![]() |
Energy Engineer How much energy do you think all the houses and buildings in the United States consume? It turns out they eat up 40% of all the energy that the U.S. uses in a year. The figure is high because all those houses and buildings need to be heated, cooled, lit, ventilated, and supplied with heated water and electricity to run all sorts of electrical devices, appliances, and computers. Energy efficiency engineers help reduce the energy that houses and buildings use. This saves families and businesses money, and lowers the emissions of greenhouse gases that contribute to global warming. | |
![]() |
Physics Teacher Our universe is full of matter and energy, and how that matter and energy moves and interacts in space and time is the subject of physics. Physics teachers spend their days showing and explaining the marvels of physics, which underlies all the other science subjects, including biology, chemistry, Earth and space science. Their work serves to develop the next generation of scientists and engineers, including all healthcare professionals. They also help all students better understand their physical world and how it works in their everyday lives, as well as how to become better citizens by understanding the process of scientific research. | |||
|
Join Science Buddies
Become a Science Buddies member! It's free! As a member you will be the first to receive our new and innovative project ideas, news about upcoming science competitions, science fair tips, and information on other science related initiatives. |