By the end of this lab, you will be able to read every part of ESRT page 3 — the Portion of the Electromagnetic Spectrum Related to Earth and Space Sciences. You will know how to find a wavelength, how to find a frequency, what region of the spectrum you are in, what color a visible wavelength represents, and which telescopes astronomers use to observe each region.
📚 Vocabulary — the words you need to talk about waves and light.
📖 Reading — how telescopes turned invisible waves into pictures of the universe.
📊 Tutorial — how to read every axis on the ESRT chart, with simulations.
🔭 Telescope Explorer — what each space telescope sees and why.
📋 Data Table — match telescopes to wavelengths.
✅ Practice — 15 chart-reading questions and 10 Regents-style questions.
🖨️ Print — your final grade report as a PDF for your folder.
How it works: Click any card to flip it. Only one card stays open at a time, and each card auto-closes after 8 seconds. Cards never lock — you can re-open any card as often as you need.
Tap a word on the left, then tap its definition on the right. Matched pairs turn green.
If you stood outside on a clear summer night and looked up at the Milky Way, your eyes would only catch a thin slice of what is actually streaming down from the sky. The pinpricks of starlight you see are visible light, and visible light makes up only a tiny portion of all the energy traveling through space. The rest of that energy — ultraviolet light, infrared light, and microwaves — is completely invisible to human eyes. To see the full picture of the universe, astronomers had to build instruments that act like new kinds of eyes.
Every type of light, visible or invisible, is part of the same family called the electromagnetic spectrum. Each member of the family is described by two numbers: its wavelength (how long one wave is, measured in nanometers or meters) and its frequency (how many waves pass a point each second, measured in hertz). Wavelength and frequency are linked. As wavelength gets shorter, frequency gets higher, and the wave carries more energy. As wavelength gets longer, frequency drops and the wave carries less energy. Ultraviolet light is short and energetic. Microwaves are long and weak. Visible light sits between them.
Astronomers do not have a single telescope that sees everything. They have a different telescope for every wavelength.
The Hubble Space Telescope, launched in 1990, sees mostly the same colors your eyes do, plus a bit of ultraviolet. Hubble took the deep field images that revealed thousands of galaxies in a patch of sky the size of a grain of sand held at arm's length. But Hubble cannot see through the dust clouds where new stars are forming. For that, astronomers needed infrared eyes.
The James Webb Space Telescope, launched in 2021, observes infrared light. Infrared waves are longer than visible light, so they slip through dust that would block visible light entirely. James Webb has shown us baby stars, swirling planet-forming disks, and galaxies so distant that their light has been stretched into the infrared by the expansion of the universe. The telescope sits a million miles from Earth and is shielded by a sunshade the size of a tennis court so its own warmth does not blind its detectors.
Even longer wavelengths require ground-based dishes. ALMA, the Atacama Large Millimeter Array in Chile, uses 66 linked antennas to detect microwave and millimeter-wave signals from cold gas clouds where stars are being born. To see the shortest, most energetic waves, astronomers use the ultraviolet detectors aboard satellites like the Solar Dynamics Observatory, which watches the Sun's roiling outer atmosphere — far too hot to glow in visible colors alone.
The chart on page 3 of your Earth Science Reference Table puts the entire spectrum on a single line. The top axis shows wavelength, measured in nanometers. The bottom axis shows frequency, measured in hertz. The visible spectrum — violet, blue, green, yellow, orange, red — is zoomed in at the top of the chart so you can see exactly which wavelength matches which color. Once you can read this chart, you can answer questions about telescopes, stars, energy, and color all from the same diagram.
Use your reading and what you know about the EM spectrum to complete the writing tasks below. Place words correctly in the scramblers (correct words turn green), and expand the simple sentences using the prompts.
"Hubble takes pictures."
"James Webb sees infrared."
"Wavelengths can be measured."
The top axis on the chart is labeled Wavelength (nm). The numbers go from 1 on the left up to 10⁹ on the right. That right end is also labeled (1m) because 10⁹ nanometers equals one meter.
The thin gray rectangle at the top of the chart is the visible spectrum. It is the tiny range from about 4.0×10² to 7.0×10² nm (400–700 nm). The dashed lines fan out to show that this thin band is being magnified to show the colors.
Look at the bottom arrow on the chart: Increasing Wavelength →. Microwaves on the right edge can be a meter long. UV waves on the left are shorter than the width of a virus.
Quick check: If a wave has a wavelength of about 5 × 10⁵ nm, what region is it in?
The bottom axis is labeled Frequency (Hz). The numbers run from 10¹⁸ on the left down to 10⁶ on the right. Notice that frequency runs in the OPPOSITE direction of wavelength.
This is the most important rule on the entire chart:
The chart marks two specific frequencies at the edges of the visible band:
Quick check: A wave has a frequency of 10¹². Which region is it in?
Before you begin: All light — visible, infrared, ultraviolet, microwaves — travels as a wave. Two numbers describe every wave. Frequency tells you how many waves pass a point each second, measured in hertz (Hz). Wavelength tells you the distance from one peak of a wave to the next, measured in nanometers (nm) on the ESRT chart.
These two numbers are linked. Because all light travels at the same speed, when frequency goes up, wavelength must go down — and the other way around. The simulator below lets you change the frequency and see exactly what happens to the wavelength.
Drag the slider below to change the wave's frequency. Watch what happens to the wavelength — and notice how the two are linked.
What to notice:
📌 Slide frequency UP → wavelength shrinks, energy goes UP.
📌 Slide frequency DOWN → wavelength stretches out, energy goes DOWN.
📌 The product of wavelength and frequency stays constant — that constant is the speed of light.
Quick check: If you double a wave's frequency, what happens to its wavelength?
Before you begin: The electromagnetic spectrum is a continuous range of light, from very long microwaves on one end to very short ultraviolet waves on the other. Every point on that spectrum has its own wavelength and its own frequency. The visible colors your eyes can see — violet through red — are only a tiny slice of the full chart on ESRT page 3.
The slider below lets you scan across the whole spectrum. As you drag the marker, the readout boxes will tell you the wavelength, the frequency, the region of the spectrum, and — if you are inside the visible band — the exact color you are pointing at.
Drag the marker across the spectrum. The readout shows what wavelength, frequency, and region you are pointing at.
Quick check: What is the approximate wavelength of green light?
Why we need different telescopes: Your eyes can only see one thin slice of the electromagnetic spectrum — the visible band, from about 4.0 × 10² to 7.0 × 10² nanometers. Almost everything else the universe emits is invisible to humans. Hot young stars blast out ultraviolet. Cold dust clouds glow in infrared. The leftover heat from the Big Bang shows up as microwaves. None of that reaches our eyes.
Astronomers solve this by building telescopes designed to capture specific regions of the EM spectrum. A telescope with the right detector can pick up wavelengths the human eye misses entirely. The Solar Dynamics Observatory was built to see ultraviolet light from the Sun. Hubble was built mostly for visible light, with some ultraviolet. James Webb was built for infrared so it can see through dust to newborn stars and distant galaxies. ALMA was built for microwaves to study cold gas where stars are forming.
The same object can look completely different in each region — that is why scientists do not rely on a single telescope. Combining views from across the EM spectrum gives a more complete picture of what is really happening in space.
Tap a telescope to learn what region of the EM spectrum it observes and what kinds of objects it studies.
Use what you learned in the Telescope Explorer above and the ESRT chart at the top of this page to fill in the table. (4 points total)
| Telescope | Wavelength Region (UV / Visible / IR / Microwaves) | Approximate Wavelength on ESRT | One Object It Studies |
|---|---|---|---|
| Hubble Space Telescope | |||
| James Webb Space Telescope | |||
| Solar Dynamics Observatory | |||
| ALMA (Atacama Large Millimeter Array) | |||
| Spitzer Space Telescope |
Use the ESRT chart shown below for every question. The chart will reappear between question groups so it is always nearby.
These questions are written in the same style and format as the New York State Earth and Space Sciences Regents exam.
Student: — | Period: — | Date:
| Section | Earned | Possible |
|---|
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