LED lights are becoming much more common. They’re used in traffic lights, bicycle lights, flashlights, message displays, and their application is growing. LED holiday lights have been available for several years; however, the sales of the LED versions lag behind the traditional incandescent lights, primarily because of cost. (LED lights can be as much as five times more expensive.) Nevertheless, LED lights have several important advantages over conventional incandescent bulbs, including
Produce less heat (more energy efficient)
Emit light of a given color without requiring a filter
Produce focused light without requiring a reflector
In the true spirit of the season, we decided to perform some tests to quantify the differences between these lighting options. We tested the “clear” C7 sized LED and incandescent bulbs.
This experiment made use of the Vernier Surface Temperature Sensor placed against the bulb halfway between the tip and the base. The Logger Pro default data-collection setup was used, collecting one sample each second for a total of 180 seconds. Data were collected for 10 seconds prior to turning on the lights.
While we expected the incandescent lights to get hot (in fact too hot to handle comfortably), we were surprised to see the virtually unchanged LED temperature.
This experiment made use of the Vernier Light Sensor set to the 0-6000 lux range. Five small holes were cut in one side of a cardboard box just large enough for the bulbs. Another small hole was cut in the opposite side of the box for the Light Sensor. Data collection was set up using Selected Events. The light intensity was measured for a single bulb, and then again as we added bulbs, one at a time, until we measured the intensity of five bulbs together. We were careful not to touch the incandescent bulbs, as the previous activity showed they get hot very quickly.
If having very bright holiday lights are a requirement, then your best bet would be to purchase incandescent lights. It should be pointed out that the incandescent bulbs had an advantage for this activity, as these bulbs were clear, smooth glass, while the LED bulbs were slightly frosted, dimpled plastic.
In this experiment, we looked at the emission spectra of the “white” light emitted by each type of bulb. The cuvette holder was removed from a Vernier Spectrometer and a bulb was positioned a few centimeters from the Spectrometer. The Logger Pro Software was set to collect Spectrometer data measuring intensity.
The results here were as expected. It is clear from the graph that the LED lights emit light over a much narrower range of wavelengths. The spike of intensity around 470 nm was consistent with the bluish appearance of the “white” LED lights.
For Further Investigation
Here are a few additional things to try…
Compare bulbs of similar color
Investigate the cost to operate the lights for several years