3B Scientific GmbH
Rudorffweg 8
21031 Hamburg
Germany
www.3bscientific.com
Subject to technical amendments
© Copyright 2015 3B Scientific GmbH
6. Experimental applications
Investigation of the inverse square law for a
point light source
Properties of polarising filters
Demonstration of the flickering effect of alter-
nating current for fluorescent lamps
Measurement of solar energy
Studies of reflection
Measurements of illuminance at work-stations
and personal areas
Relationship between light intensity and growth
of plants
7. Sample experiment
Investigation of the inverse square law for a
point light source
Apparatus needed:
1 3B NET
log
TM
@ 230 V
1000540
or
1 3B NET
log
TM
@ 115 V
1000539
1 3B NET
lab
TM
1000544
1 Light sensor
1000562
1 Experimental lamp, halogen
1003038
1 Transformer @ 230 V
1000593
or
1 Transformer @ 115 V
1006780
1 Barrel foot
1001045
1 Vertical ruler, 1 m
1000743
2 Universal clamps
1002830
Set up the experiment as shown in Fig. 1.
On the 3B NET
lab
TM
, open the application
program (template) for the experiment with
the light sensor.
Lay the ruler horizontally, and fix the exper-
imental lamp at the 15 cm mark using one
of the universal clamps.
Define this point as distance zero, 0.
Mount the light sensor on the ruler using
the other universal clamp.
Connect the electric cables to the experi-
mental set-up and switch on.
Start the template program, select “manual
input”, and measure the light intensity at
the first point, a distance of 5 cm in front of
the experimental lamp.
Increase the distance in steps of 5 cm up
to the 70 cm mark (a distance of 55 cm
from the experimental lamp), and record
the corresponding light intensities in the
3B NET
lab
TM
(Fig. 2).
Generate the data curve using the “Fit”
function.
Fig. 1 Investigation of the inverse square law for a
point light source
Fig. 2 Plot of the data points from the inverse
square law experiment on the monitor screen
of the 3B NET
lab
TM
