10
Capturing Light
Subject: Physics
Sensor: SmartEye sensor
Aim:
To show that the apparently continuous light emitted from a fluorescent lamp is not constant but fluctuates.
Overview:
When you look at light coming from a fluorescent or standard lamp, it appears to be constant in terms of its output. What actually happens can be
quite surprising. Using the SmartEye sensor, LogIT Black Box and the fast triggered function of the logging software, the output of a fluorescent lamp
can be captured.
Equipment required:
LogIT Black Box.
SmartEye light sensor.
Light source such as a fluorescent lamp.
Black card or human finger.
Infrared remote control (Extension activity).
Hazards:
Students should be supervised at all times.
Do not look directly into the light from the lamp.
Allow the lamp to cool before handling in any way.
Always check your local regulations or the school advisory service such as CLEAPSS or SSERC
for guidance on the use of any hazardous material or source.
Setup:
1. Connect Black Box to the computer using the USB cable.
2. Plug the SmartEye sensor into any channel of Black Box.
3. Start LogIT Lab software.
4. Click ‘Setup’ then select ‘Fast with trigger (one sensor only)’ and click ‘Next’
5. Select ‘500 microseconds for 0.1 seconds’ as the log rate and interval then click ‘Next’ followed by ‘Finish’.
Note: Depending on the brightness of the lamp you may find that the finger over the end of the sensor is sufficient to keep the logger from
triggering early. If not, use a thick piece of black card. If using other datalogging software, set the logging interval to 500 microseconds.
The photo shows an energy saving fluorescent lamp being used which worked well using a 500 microsecond logging interval.
Note that some energy saving bulbs have complex electronics which can remove the flicker and may not be suitable.