When an LED is submerged in liquid nitrogen, its emitted light shifts in color.

1. Connect an LED to a safe low-voltage battery circuit.
2. Confirm the LED is lit at room temperature and note its color.
3. Wearing cryogenic gloves and safety glasses, carefully immerse the lit LED into a container of liquid nitrogen.
4. Observe the change in color (typically a shift toward higher-energy light, e.g., orange → yellow, yellow → green).
5. Remove the LED from liquid nitrogen and watch it return to its original color as it warms.

Why Do Yellow LEDs Change Color in Liquid Nitrogen? - Baltic Lab:

📄 The Physics Well: https://the-physics-well.net/its-not-easy-explaining-green/

📄 Why LED light changes color when dips into liquid nitrogen? - Stack Exchange: https://physics.stackexchange.com/questions/611567/why-led-light-changes-color-when-dips-into-liquid-nitrogen

• Try different colors of LEDs (red, green, blue) to see how the degree of color shift differs.
• Compare inorganic semiconductor LEDs with organic LEDs (OLEDs), which may show opposite behavior due to molecular effects.
• Use a spectrometer or diffraction grating to measure the wavelength shift more precisely.

• Safety glasses required.
• Wear cryogenic gloves when handling liquid nitrogen.
• Ensure electrical leads are insulated and avoid short circuits in the presence of liquid nitrogen.
• Use only in a well-ventilated area to prevent nitrogen gas buildup.
• Never submerge batteries or power sources - only the LED and wires should contact the liquid nitrogen.

• Why does lowering temperature increase the band gap in semiconductor LEDs?
• How does a larger band gap lead to higher-energy (shorter wavelength) photons?
• Why might organic LEDs (OLEDs) show a red-shift instead of a blue-shift when cooled?
• What real-world technologies depend on the temperature sensitivity of semiconductors?
• How could this experiment be used to introduce the concept of the quantum nature of light?