Spectrum and color production- prisms

Which color light carries more heat energy?

Introduction: (Initial Observation)

For many of us our first observation of light spectrum has been a rainbow. Later you may have noticed similar effects when light passes trough or reflects by a glass object. In this project you will create a light color spectrum and study the properties of individual light colors in the light spectrum.

Information Gathering:

Find out about color lights and their properties. Find out how different are different color lights. Read books, magazines or ask professionals who might know in order to find out how different color lights may be produced. Keep track of where you got your information from.

Following are samples of information that you may find:

Following are some useful links:

http://home.att.net/~RTRUSCIO/SPECTRUM.htm

http://www.centralsquareschools.org/brewerton/artwork/prism.html

http://heasarc.gsfc.nasa.gov/docs/xte/learning_center/universe/prism.html

http://cse.ssl.berkeley.edu/lessons/indiv/nellie/em_prism.html

http://fuse.pha.jhu.edu/~wpb/spectroscopy/measure.html

http://hubble.stsci.edu/sci.d.tech/nuts_.and._bolts/spec101.shtml

http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html

Project plan:

Use a prism to create a color Spectrum. Then use the color spectrum to perform some other experiments such as measuring the temperature in different areas of the color spectrum. Finally try to answer some of your questions about light and color using your observations during your experiment.

Life applications:

Practical applications of light and light spectrums well exceed thousands of pages.

After people discovered that red and infrared lights are the warmest, they made thousands of devices based on red and infrared radiations. Among those are heat lamps, Remote controls for TVs and night vision cameras.

Discovery of cold ultra violet light lead to invention of UV lamps used to identify minerals, counterfeit bills, detect invisible stains, kill bacteria, do chemical reactions, make printing plates and many more…

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

What is the relation between heat in the sunlight and different colors in the light spectrum? (Do all color lights have the same amount of heat energy?)
This will be the main question of this project.

Is there any relation between refraction and color spectrum? (Do some colors bend more than other colors?)

You may come up with other questions and similar experiments.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

The independent variable is the color of light produced in a color spectrum. We use a prism to create a color spectrum.

The dependent variable is the heat energy of each color light. We will measure the temperature in each color light area as a representation for the heat energy.

Controlled variables are air flow and ambient temperature (room temperature).

Constants are:

• The light source. Use sunlight.
• The prism used to produce the light spectrum.
• Experiment method and time.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. A sample hypothesis for first question is:

I think red and yellow colors should be the warmest colors. My hypothesis is based on my observation of sunlight that is almost yellow and heat lamps that are usually red.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1:

Heat energy of different color lights

Introduction: In this experiment we pass sunlight through a prism. As sunlight passes through the prism, the prism divides it into a rainbow of colors called a spectrum. A spectrum contains all of the colors which make up sunlight. Now we want to measure the amount of heat in each color. To do this we use thermometers with blackened bulbs and measured the temperature of the different colors of the spectrum.

Materials: For this experiment you need an equilateral glass prism, 3 alcohol thermometers, scotch tape, a white piece of paper and a south facing window sill or a box. All these products are available at MiniScience.com and many other science suppliers.

Procedure: You will need to blacken the bulbs of the thermometers so it will absorb the light, otherwise it will reflect part of light and the experiment will not work. To do this cover the thermometers with masking tape exposing only the bulbs and then spray paint

In the above image you can see how to set up this experiment for outdoors. We placed a white piece of paper at the bottom of a cardboard box. Next we rotated the prism until a good wide spectrum appeared on the white paper at the bottom of the box and then taped the prism into place. To get a good spectrum we had to tilt the box up on the prism end by placing a rock under it.

First check the temperature of the thermometers away from the spectrum in the shaded area of the box. The above image shows the temperature before the thermometers are placed in the spectrum. All 3 read 76 degrees which is the outdoor shade temperature.

Now let’s place the thermometers in the spectrum. We will place the left bulb in the blue part of the spectrum, the middle bulb in the yellow part of the spectrum, and the right bulb just past the red part of the spectrum in a region where there is no visible light.

The right image shows the temperature readings after about 1 minute. It takes a few minutes for the temperatures to reach their final value. Within 1 minute you can already see a difference in temperature. The thermometer in the blue part of the spectrum shows the lowest reading which is not much higher than shade temperature. The yellow part of the spectrum is showing a much higher temperature than the blue. The thermometer on the right, which is in the dark region just past the red, is showing the highest temperature of all 3 regions. (The sun had moved slightly by the time this picture was taken, and hence the right-most bulb just started to have a small portion of the red spectrum shining on it then.)

The differences between the 3 temperature readings continue to grow larger until the final temperatures are reached (shown above). You can now see that the dark area shows a much higher temperature than the areas which are in regions of light. Final readings are:

Final readings are:
blue: 80 degrees yellow: 83 degrees infrared: 86 degrees

Data table:

Record your results in a table showing the ambient temperature and the maximum temperature in different color lights. The ambient (No light) temperature is the temperature showed by your thermometers before placing them in any color light. The temperature increase is in relation to the ambient temperature. Your results table may look like this:

Make a graph:

Create a bar graph with 4 vertical bars. Name each bar with the specific color light it represents. For example you may name them as Infra red, Red, Yellow, and Blue. The height of each bar represents the temperature increase caused by that color. Write the actual amount of temperature increase above or on each bar. It is best if you color the bars the same as the color light they represent.

Notes:

1. The differences between the temperatures of the colors of the spectrum vary with the width of the spectrum, which depends on time of day, and the distance from the prism, which is proportional to the height of your box. In all cases the trend of temperature increasing from blue to infrared should still show up.

2. All the wavelengths farther than the infrared are compressed to a small region just beyond the red. For typical box depths of 0.3 m, no solar wavelengths are beyond 0.4 cm from the end of the red, so the “infrared” thermometer must be placed immediately next to the end of the observed spectrum.

3. If you can arrange to have the prism more distant from the projected spectrum, the wavelengths will be spread out farther, giving more room to explore the infrared. However, the difference in the thermometer readings will be smaller since they will intercept less energy.

A similar experiment by Sir William Herschel In the year 1800 lead to discovering the existence of infrared. This experiment was important not only because it led to the discovery of infrared light, but also because it was the first time that someone showed that there were forms of light that we cannot see with our eyes. As we now know, there are many other types of light that we cannot see and the visible colors are only a very small part of the entire range of light which we call the electromagnetic spectrum.

Experiment 2:

Newton’s Blue Light Experiment

Many of Newton’s experiments were performed using prisms (which were pretty new at that time). Grimaldi and others knew that when white light was directed into a prism, a pattern of brilliant colors came out the other side (as shown in the picture below). But how did this work? And did it help understand color and light?

To find out, Newton took this one step further by selecting out only blue-colored light coming from one prism and passing it through a second one. He thought this would help decide how prisms produced the different colors. You can try Newton’s experiment yourself. The diagram and picture below shows how to set it up.

DIAGRAM OF SET-UP:

PICTURE OF SET-UP: Light from the first prism is coming from the left and hitting the two sheets of paper.

RESULTS: The blue portion goes through the slit and goes through the second prism, creating a blue band on the far sheet of paper. Here’s a better picture of what it looked like in the darkened room:

Newton’s Explanation For This

Newton noticed that when he passed only the blue portion of the light into the second prism, only blue light came out. According to Aristotle and Kepler, the blue light should have been changed more by passing it through another prism — but it wasn’t! The light entering the second prism looked the same as the light coming out. Newton explained this by thinking of the blue light as a particular kind of light. Looking back to the first prism which was producing a rainbow of colors using only white sunlight, Newton proposed the idea that white light is actually a mixture of different colors of light

Materials and Equipment:

The most important piece that you need for this project is a prism. Glass and clear plastic prisms are available at prices of $5 to $10.

Glass Prism and Thermometers at MiniScience.com

See a sample of equilateral 25 mm, Length 75 mm prism part # GPRISM25

See a sample of glass thermometer Part# GATW_1

Other materials include a box, some adhesive tape and one or more thermometers.

What if I cant find a prism?
If you can not find a plastic or glass prism, you can still produce a similar result using water prism. Try this:

1. Cover the small pocket mirror with wraps of the black electric tape, leaving a one six-tenths inch slit between two wraps near one end of the mirror. Next, place the mirror in a dish in an angle with the slit down near the bottom of the container. Add water until the slit is covered by an inch of water.
2. Turn the glass so the mirror is facing the sun.
3. Hold the paper at a slant in front of the glass. Move the paper around until you the rainbow colors. You may need to move the paper around slightly until the colors come into full focus.

What you are seeing is the various wavelengths of light broken apart. Sunlight is comprised of 7 different colors. A light bulb actually produces more red and orange colors. A fluorescent light has more blue and yellow.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

In our experiment we notice that the temperature increases from the blue to the red part of the spectrum. Then we placed a thermometer just past the red part of the spectrum in a region where there was no visible light and found that the temperature there was even higher. So there must be another type of light which we cannot see in this region. This light is called infrared.

Calculations:

We did not need any calculation in this project.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Sample questions

1. In what order will the colors in the rainbow (or visible spectrum) appear?
2. What colors of the rainbow will be visible with the various filters?
3. Are all color bands the same thickness?
4. Now, check the positions of the colors by looking at them through the color filters. If the filter were merely coloring the light, wouldn’t it change the blue light into red light? Instead, the blue light is clearly blocked out.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List your printed and online references here.