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CBL
Lab 1

AC Light with the CBL 

7/1/99

Purpose: 

You will use a CBL with a light probe to observe how light intensity varies over time for light sources powered by AC electricity and determine the freqency of the variation.

Equipment / Materials:

TI-83 Calculator TI link cable CBL light probe

CBL TI PHYSICS program group light sources (incandescent or fluorescent)

Equipment/Software Setup:
  1. Using the adapters, plug the light detector into channel 1 of the CBL.
  2. Obtain the TI program group PHYSICS from someone else via your TI link.
  3. Attach your TI-83 to the CBL using your TI link; make sure that this connection is secure.
  4. Plug the CBL ac adapter into the wall outlet and turn on the calculator and CBL.
  5. Now your task is to set up the calculator/CBL to collect light intensity data:

Access and run the program PHYSICS.

Get to the Main Menu of the PHYSICS program

Choose SET UP PROBES from the Main Menu.

Enter 1 for number of probes.

Select MORE to see a continuation of probe choices and then choose LIGHT.

Choose COLLECT DATA from the Main Menu.

Select TIME GRAPH from the Data Collection Menu.

Enter 0.001 for the time between samples.

Enter 100 for the number of samples.

The selected experiment length with be displayed.

Hit [ENTER]. Then, from the Continue Menu, select MODIFY TIME SETUP if you need to make changes or USE TIME SETUP if you are satisfied.

Collecting/Analysing the Light Data:
  1. Turn on your light source.
  2. Hold the probe end near the light source so that the probe is aimed directly at the light source. Isolate the probe from all other sources of light.
  3. Hit [ENTER] on the calculator to start to collect the light data.
  4. In a few seconds, the list locations of the data will be given. In the case of this experiment, L1 is time in sec, L2 is intensity.
  5. Hit [ENTER] and a graph of intensity versus time will appear on the screen. The graph should show a repetitive pattern but will likely not be a smooth waveform. . If you like the data you see, proceed to the next step. If you are unsatisfied with this set of data, follow the program menus until you get the option to recollect data in the <REPEAT?> menu. Hints: If the light is too bright, the graph may look flat--use a dimmer light or move it away from the probe a little. If the light is too dim or other lights are interfering with the measurement, the graph will look random--move the probe closer and get rid of extra sources of light.
  6. Record the light source you used to produce the data.
  7. In the box provided, draw and label the complete graph display.
  8. In order to obtain the most accurate measure of the period, how many complete cycles should be used for the calculation--only one or several? Why? Use the left and right arrow keys on the calculator to find the time values needed to determine the period. Use *’s to clearly mark the two positions on the graph that you used to determine the wave period. Show your complete calculation of the period.
  9. Once you have a value for the period, invert this value and thus find the frequency.
  10. Repeat the collection and analysis for several different provided light sources.

 

 

report form for Name:_______________________________

AC light with the CBL Period:___________ Date:_______________

LIGHT SOURCE #1:

Light Source #1 was __________________________________________

graph....

calculations:

 

 

 

period = _____________seconds

 

frequency = ____________Hertz

LIGHT SOURCE #2:

Light Source #2 was __________________________________________

graph....

calculations:

 

 

 

period = _____________seconds

 

frequency = ____________Hertz

LIGHT SOURCE #3:

Light Source #3 was __________________________________________

graph....

calculations:

 

 

 

period = _____________seconds

 

frequency = ____________Hertz

LIGHT SOURCE #4:

Light Source #4 was __________________________________________

graph....

calculations:

 

 

 

period = _____________seconds

 

frequency = ____________Hertz

LIGHT SOURCE #5:

Light Source #5 was __________________________________________

graph....

calculations:

 

 

 

period = _____________seconds

 

frequency = ____________Hertz

 

 

Question 1: In order to obtain the most accurate measure of the period, how many complete cycles should be used for the calculation--only one or several? Why?

 

 

 

 

 

 

 

Question 2: What do you notice about the values of the frequencies for the different light sources? Attempt an educated guess how it happens this way. Propose another type of measurement that could be made to perhaps support or refute your explanation.

 

 

 

 

 

 

 

 

 

 

Question 3: Does the brightness of the light source go away completely between the high points on the intensity versus time graph? Attempt an educated guess how it happens this way.

 

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