By Oksana Love
Sunlight contains an electromagnetic spectrum (special waves such as the kind in x-rays that travel through emptiness or a vacuum) of light that stretches from very short gamma rays to very long radio waves. Humans can only detect a tiny portion of this spectrum. This is known as visible light, and it is what allows us to see different colors.
Have you ever wondered how it would be to see beyond the visible spectrum like some snakes or insects do? Let’s look at some pictures in the near-infrared (IR) spectrum that you can’t observe using the naked eye. Using IR, there’s a whole new world to look at!
Safety Suggestions
- Safety goggles required
- Protective clothing suggested
- Caution: hot liquids!
- Do not eat or drink any of the materials used in this activity
- Thoroughly wash hands after this activity
Materials
- Smartphone that can take pictures with long exposures (most phones can do this using their camera’s “night mode” setting)
- Infrared Filter
- Clear tape
- Scissors
Procedure
- This activity is best performed outside, on a bright, sunny day.
- Before starting the activity, pick a bright spot outside. Use your phone to take a normal picture using visible light.
- Next, use a piece of tape to attach the filter to the phone, covering all its lenses.
- Now set up your phone’s camera to work in “night mode.” Then take the same picture you took in step 2 — but this time, give it the longest exposure your phone allows. Try to hold your phone steady while taking the picture.
What did you observe?
What colors did you observe? Describe what you see. | |
Visible light (normal picture) | |
Near-IR light (picture with filter) |
How does it work? / Where's the chemistry?
Visible light is just a small portion of the whole electromagnetic spectrum. In this part of the spectrum, different wavelengths will give off different colors, which we can observe. But infrared (IR) light is beyond the end of the visible spectrum, so we cannot see it with our eyes. The filter that we used in this activity blocked almost all visible light, allowing us to see the picture in the near-IR range. Since the near-IR range is the closest in wavelength to the red color in the visible spectrum, the picture will have a red tint.
Oksana Love is an Assistant Professor at the University of North Carolina Asheville.
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