Best examples of investigating light with homemade spectroscopes

Starting with simple examples of investigating light with homemade spectroscopes

Before we talk theory, let’s start with concrete, real-world examples of investigating light with homemade spectroscopes. These are the kinds of experiments that make students’ eyes light up (literally and figuratively):

You build a spectroscope from a paper towel tube, a slit cut in aluminum foil, and a scrap of diffraction grating from an old DVD. Then you point it at a warm white LED bulb and see a smooth rainbow with some colors brighter than others. You try it on a compact fluorescent lamp and suddenly the rainbow breaks into sharp, bright lines. Same room, same outlet, completely different spectral “fingerprints.”

Or you step outside on a clear day, point your homemade spectroscope near (but not directly at) the sky close to the Sun, and compare that spectrum to the one from your phone’s flashlight. Both look like rainbows, but they are not identical. Those differences are the heart of every good example of investigating light with homemade spectroscopes: you’re comparing how different light sources spread out into color.

These first experiments are the hook. Once students see that not all white light is the same, they’re ready to go deeper.

Building your homemade spectroscope for repeatable experiments

To get reliable examples of investigating light with homemade spectroscopes, you want a design that’s simple, sturdy, and easy to rebuild. A common classroom favorite uses:

• A cardboard tube (shipping tube or paper towel tube)
• A narrow slit made from two pieces of aluminum foil or black cardstock
• A small piece of diffraction grating film (often 500–1000 lines/mm)
• Tape and scissors

You cover one end of the tube with foil, cut a thin vertical slit (about the width of a razor blade), and tape the diffraction grating at the other end at a slight angle so you can look through it comfortably. That’s it.

For a more precise setup, many teachers and students now use low-cost diffraction grating sheets ordered online and 3D-printed holders to control the angles. Physics departments and teacher resources from universities like the University of Colorado Boulder and MIT OpenCourseWare often share printable patterns and lesson ideas for this kind of build (for example, see the physics education materials at https://phet.colorado.edu).

The key is consistency: the same spectroscope used across all your trials makes your examples of investigating light with homemade spectroscopes more convincing and easier to compare.

Classic classroom examples of investigating light with homemade spectroscopes

Teachers around the world use similar setups, and over time a few “best examples” have emerged because they show clear, dramatic differences.

Comparing household light bulbs

One powerful example of investigating light with homemade spectroscopes is a simple “mystery bulb” challenge. You gather several everyday light sources:

• Incandescent bulb
• Compact fluorescent lamp (CFL)
• Warm white LED bulb
• Cool white LED bulb
• Halogen work light

Students look at each source through the same spectroscope and sketch what they see. Incandescent and halogen bulbs usually show a continuous spectrum: a smooth rainbow from red through violet, because the filament is essentially a hot blackbody radiator. In contrast, CFLs and some LEDs show bright bands or uneven intensities because they rely on specific electronic transitions and phosphors.

Without showing the labels, you ask students to match each spectrum sketch to the correct bulb type. This is one of the best examples of how a homemade spectroscope can turn a guessing game into evidence-based reasoning.

Sunlight versus indoor lighting

Another classic example of investigating light with homemade spectroscopes is comparing natural daylight to indoor light. On a clear day, students view the sky near the Sun (never directly at the Sun) and sketch the spectrum. Then they go indoors and look at a classroom LED fixture.

Both look “white” to the eye, but the spectra are different. Daylight tends to be smoother and broader. Many white LEDs, on the other hand, show a strong blue spike plus a broader yellow-green region from the phosphor. This leads to great discussions about color temperature, why some rooms feel “cool” or “warm,” and how lighting design has changed as LEDs have replaced older bulbs.

For background on visible light and color, students can read accessible explanations from NASA’s science education pages, such as the material on the electromagnetic spectrum at https://science.nasa.gov/ems.

More advanced examples include gas discharge tubes and line spectra

Once students are comfortable with everyday sources, you can move on to more advanced examples of investigating light with homemade spectroscopes using gas discharge lamps. Many high school and college labs use these to introduce the idea of quantized energy levels.

Common gases include:

• Hydrogen
• Helium
• Neon
• Mercury vapor

When viewed through a homemade spectroscope in a darkened room, each gas shows a distinctive pattern of bright colored lines. Hydrogen, for example, shows a famous set of red, blue-green, and violet lines known as the Balmer series. These are the same patterns that astronomers use to identify elements in stars.

Even if you don’t have lab-grade gas tubes, you can still find real examples in everyday life. Many older streetlights and some decorative signs use sodium or mercury vapor lamps, which show strong yellow or blue-green lines. Students can sketch these and compare them to reference spectra from university physics departments or NASA’s astronomy education pages.

This set of experiments turns your collection of examples of investigating light with homemade spectroscopes into a bridge between classroom physics and professional spectroscopy used in astronomy and chemistry.

Digital-age twist: using phone cameras and software in 2024–2025

In the last few years, one of the best examples of bringing this project up to date has been combining homemade spectroscopes with smartphones. Students still build the basic tube-and-grating device, but they align the diffraction grating with a phone camera instead of their eye.

With a bit of practice, they can capture photos of each spectrum and then analyze the images with free or low-cost software. Some options include open-source image analysis tools from universities and citizen science platforms that let users share spectra and compare results. Many physics educators now encourage this approach because it makes the data easier to archive, measure, and present at science fairs.

By 2024–2025, this has become one of the most popular examples of investigating light with homemade spectroscopes in STEM clubs and online maker communities: students build, photograph, upload, and compare spectra from around the world. They might even compare their LED bulb spectra to published reference data from research institutions or educational resources, such as the spectroscopy tutorials hosted by major universities.

Creative project ideas: best examples for science fairs

If you’re planning a science fair project, you want examples of investigating light with homemade spectroscopes that go beyond “look at this rainbow.” Here are several project directions that have worked well for middle and high school students:

1. Comparing different brands of “daylight” LEDs

Students collect several brands and color temperatures of LED bulbs marketed as “daylight” or “warm white.” They record spectra for each and look for patterns: Which ones have the strongest blue spike? Which have smoother coverage in the green and red? They can then connect this to comfort, eye strain, or energy efficiency, referencing general lighting and eye health information from sources like the U.S. Department of Energy or educational health sites such as https://www.nih.gov.

This is a strong example of investigating light with homemade spectroscopes because it ties consumer products, data, and human experience together.

2. Screen colors and digital displays

Another engaging example of investigating light with homemade spectroscopes focuses on screens. Students view a phone, tablet, or laptop screen showing pure red, green, and blue. Through the spectroscope, they see narrow peaks instead of broad rainbows, revealing how displays use three primary colors to build every other color.

They can compare an older LCD monitor to a newer OLED display and see how the spectra differ. This leads naturally into discussions about color mixing, display technology, and why some screens look more vivid than others.

3. Outdoor lighting survey

Students take their spectoscopes on a nighttime walk (with adult supervision) and record spectra from different streetlights, storefront signs, and car headlights. They sketch or photograph the spectra and then classify the lights: LED, sodium vapor, halogen, and so on.

This real-world survey becomes one of the best examples of investigating light with homemade spectroscopes because it shows how cities are transitioning from older, narrow-spectrum lamps to broad-spectrum LEDs. It also connects directly to current trends in urban planning and light pollution research, which organizations like the International Dark-Sky Association discuss in detail.

4. Measuring the effect of filters and sunglasses

In this project, students place different filters—colored plastic, polarizing film, or sunglasses—in front of a light source. They record the spectrum before and after each filter. Some sunglasses, especially blue-light-blocking types, visibly reduce certain wavelengths.

This is a practical example of investigating light with homemade spectroscopes that connects directly to everyday questions: Do blue-light glasses really change the light reaching your eyes? Students can compare their spectra with general information about blue light and eye health from educational resources like Mayo Clinic’s vision pages at https://www.mayoclinic.org.

5. Monitoring plant grow lights

With indoor gardening and hydroponics gaining popularity, another timely example of investigating light with homemade spectroscopes is analyzing plant grow lights. Many grow lights use intense red and blue LEDs. Through the spectroscope, these show up as strong peaks in specific regions.

Students can compare “full-spectrum” grow lights to red/blue-only designs and relate their findings to basic plant biology and photosynthesis, using resources from university agriculture extensions or sites like the USDA.

How to record and analyze your spectra like a scientist

Strong science fair projects are not just about flashy examples of investigating light with homemade spectroscopes; they’re about organized data.

Students can:

• Draw each spectrum by hand in a notebook, labeling which light source it came from.
• Use a printed template with a horizontal line for the spectrum and spaces for notes on color intensity and pattern.
• If using a phone camera, keep the same camera settings and distance for each photo to make comparisons fair.

Some ambitious students estimate wavelengths by matching their spectra to published reference charts from physics departments or from educational pages on the visible spectrum, such as those linked by NASA or major universities. While homemade spectroscopes are not precision instruments, they can still show relative positions of colors and help students understand the layout of the visible spectrum.

Encourage students to organize their best examples of investigating light with homemade spectroscopes into tables: one column for the light source, one for a quick sketch or photo, and one for observations (continuous vs. lines, bright regions, missing colors). That structure makes it easier to turn raw observations into a clear science fair board or lab report.

Connecting your project to real-world science

The magic of these projects is that they’re miniature versions of what scientists do with professional spectrometers. Astronomers use spectra to figure out what stars are made of and how fast galaxies are moving. Environmental scientists analyze spectra to measure air pollution. Medical researchers use spectroscopy for everything from blood analysis to imaging.

When students build a cardboard spectroscope and collect their own spectra, they’re practicing the same basic method: split light, record the pattern, and infer what’s going on at the source.

For students who want to push further, many university physics and astronomy departments share outreach activities and background reading on spectroscopy. For instance, NASA’s astronomy education resources and physics outreach pages at major universities (such as Harvard’s science education materials at https://www.harvard.edu) explain how line spectra identify elements in stars and nebulae.

By framing your best examples of investigating light with homemade spectroscopes as miniature versions of professional techniques, you give your project a stronger story and show judges that you understand the bigger picture.

FAQ: common questions about homemade spectroscopes and examples of light investigations

How accurate are homemade spectroscopes compared to professional ones?
They’re not nearly as precise in terms of exact wavelength measurements, but they’re excellent for showing patterns: continuous versus line spectra, relative brightness of colors, and differences between light sources. For a science fair, the goal is usually pattern recognition and explanation, not laboratory-grade numbers.

What is one simple example of investigating light with homemade spectroscopes for younger students?
A great starter example is comparing a flashlight covered with white paper to the same flashlight covered with red or blue cellophane. Students look at each through the spectroscope and see how the filter removes parts of the spectrum. It’s visual, quick, and easy to explain.

Which light sources give the clearest examples of line spectra?
Gas discharge tubes (hydrogen, helium, neon, mercury) give very clear line spectra. In everyday life, some neon signs and certain older streetlights also show strong lines. These are some of the best examples of investigating light with homemade spectroscopes if you want dramatic, textbook-style spectra.

Can I safely look at the Sun with a homemade spectroscope?
No. You should never look directly at the Sun with a spectroscope or any optical device. Instead, look at reflected sunlight (for example, light off a white wall) or at a bright patch of sky away from the Sun. Safety guidelines for eye protection are also emphasized by health organizations and medical resources such as those at NIH and Mayo Clinic.

How can I make my science fair project stand out if many students use similar examples of spectroscopes?
Focus on a clear question and organized data. Instead of just showing spectra, ask something specific, like “Do different brands of blue-light-blocking glasses remove the same part of the spectrum?” or “How do streetlight spectra change across my town?” Then use your homemade spectroscope to collect data that answers that question. Judges appreciate a strong question, consistent methods, and thoughtful conclusions, even with simple equipment.

By choosing focused, real-world examples of investigating light with homemade spectroscopes and presenting them clearly, you turn a cardboard tube and some diffraction film into a surprisingly powerful scientific tool.