Summary

In this activity, students will use a phone camera to see the infrared light emitted by a television remote. They will use the electromagnetic spectrum to compare the energy of infrared light to visible light and make conjectures related to other types of light.

Grade Level

High School

NGSS Alignment

This activity will help prepare your students to meet the following scientific and engineering practices:

• HS-PS4-4: Evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.
• Scientific and Engineering Practices:
  • Asking Questions and Defining Problems
  • Planning and Carrying Out Investigations
  • Engaging in Argument from Evidence

Objectives

By the end of this activity, students should be able to:

• Compare infrared light to other forms of electromagnetic radiation.
• Construct an explanation for why infrared light is visible through a lens but not with the naked eye.

Chemistry Topics

This activity supports students’ understanding of:

• Electromagnetic Spectrum
• Radiation
• Visible Light

Time

Teacher Preparation: 10 minutes
Lesson: 30 minutes 

Materials

• TV remote
• Cellphone camera

Safety

• No specific safety precautions need to be observed for this activity.

Teacher Notes

• This activity was created in support of the 2024 National Chemistry Week (NCW)­ celebration. NCW is celebrated the week of October 20–26, 2024 with the theme, “Picture Perfect Chemistry.” Through this theme, students, teachers, and all those interested are encouraged to explore the chemistry of photography and imaging.
• An effective use of this activity could be to implement it in class as a guided activity with multiple opportunities for class-wide and small group discussion.
• The AACT animation, the Electromagnetic Spectrum, is a good precursor to this activity.
• If needed, this activity can take place partly at home. Students can investigate the phenomena using a remote control at home, along with recording their observations and inferences. Teachers can conclude the activity in class with discussion about the electromagnetic spectrum. Alternatively, if students do not have access to a TV remote and/or a smartphone camera, teachers can prepare a video to show the phenomenon in the classroom.
• When this activity was designed, this phenomenon worked with several different types of TV remotes and smart phones. However, keep track of any students who report that it does not work. Creating a prerecorded video could also be beneficial in the case that it does not work as intended from some students.
• After completing question 5, review the electromagnetic spectrum with students (on the student handout) and discuss the types of light. Ask students to locate red light (from the visible range) on the diagram and then advise them to look at the types of light with wavelengths closest to red. This should help them deduce that remotes use infrared light.
• This activity was designed for students to have the opportunity to investigate the phenomenon related to using infrared light for data communication. If students are interested in a more thorough explanation of why a camera shows the red light from the infrared spectrum, students could delve in to the physics of lenses and the mechanics of a cellphone camera. For the purpose of this activity, when asked to propose an explanation, students can keep it much simpler. A proposed explanation need only include the fact that the camera converts the IR light into red light when it creates the image. For more information, visit the Physics LibreTexts page and research optical instruments.
  • Watch out for the misconception of equating IR light with red light.
  • Emphasize that IR light is outside of the wavelength length for visible that we can typically see, but that a phone camera takes in IR light and display that light in the visible light range.
• An interesting extension would be to ask students to explain how the number of electron transitions explains how dim/bright the light from the remote is. While the distance an electron travels from one energy level to another corresponds to the amount of energy light has, the number of electron transfers affects how bright the light we see is. When multiple electrons release similar amounts of energy as they relax back down to lower energy levels, we will see brighter light as the photons all have similar wavelengths. It may help to have students compare types of remotes, or recorded videos to see if some remote lights appear brighter.