Infrared spectroscopy facts for kids

This picture shows the electromagnetic spectrum, with infrared light next to the light we can see.

Infrared spectroscopy is a cool science method that uses infrared light. Think of infrared light as a type of light we can't see, like the heat from a TV remote. Scientists use this method to study different substances. It helps them figure out what a substance is made of, or how its parts are put together. It's a bit like using a special flashlight to see hidden clues about chemicals!

This method usually uses infrared light with a wavelength between 800 nanometers and 1 millimeter. A similar method called Raman spectroscopy can also give similar results. Today, a common way to do infrared spectroscopy is called Fourier transform infrared spectroscopy.

How Does Infrared Spectroscopy Work?

Every molecule is made of atoms connected by chemical bonds. These bonds are always moving, stretching, and bending, like tiny springs. These movements are called molecular vibrations.

Each type of chemical bond vibrates at its own special speed or frequency. When infrared light shines on a sample, the molecules in the sample can absorb some of this light. They only absorb light that has the exact same frequency as their own vibrations.

An IR spectrometer is the machine that does this. It sends infrared light through a sample. Then, it measures which specific frequencies of light were absorbed by the sample.

What Can We Learn from Infrared Spectroscopy?

When a molecule absorbs infrared light, it means its vibrations have changed. This change tells scientists a lot! If a molecule's vibration causes a change in its electric charge (called a dipole), it will absorb the light. Most molecules vibrate at frequencies that match infrared light.

This method is often used to study organic compounds. These are molecules that contain carbon, like those found in living things. The spectrometer creates a "fingerprint" of the sample. This fingerprint shows all the frequencies of light that were absorbed.

By looking at this unique fingerprint, scientists can:

• Identify chemical groups: They can tell which types of chemical bonds are present in the sample. For example, if there's water in a sample, the spectrometer will show a specific signal for the O-H (oxygen-hydrogen) bond.
• Check purity: It can also show if a sample is pure or if it has other substances mixed in.

Images for kids

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  The OVIRS instrument on the OSIRIS-REx space probe uses visible and infrared light to study asteroids.

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  A typical cell used to hold liquid samples for infrared spectroscopy.

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  A scientist using a portable infrared device to check substances.

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  A diagram showing how light pulses are used in a type of infrared spectroscopy.

See also

In Spanish: Espectroscopía infrarroja para niños