2ndSem.-Physics
Light and Optics - Instructor
LO-Lab#04
Lab #LO4 - Equipment
Put the following equipment on the equipment table:
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Meter sticks and half-meter sticks
Box of 25 W replacement frosted light bulbs for table lamps (#57)
2 2-liter plastic pop bottles (#73)
Small container of red food coloring (#73)
Styrofoam cups marked with values: 0, 1, 2, 3, 4, 7, 10, 13, and "unknown" (#73)
There should be 5 cups of each.
Stack of paper towels (#36)
Each station needs the following:
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2 Small work lamps (#56)
Box of 6 crayons (red, orange, yellow, green, blue, and purple) (Ferg 302 and #61)
Pasco colorimeter (#21) plugged into channel A (should have LED display screen)
2 plastic cuvettes with lids (#21)
1 paper handout on making graphs with Excel (Instructor's manual)
1 large green plastic tub (#5) (1 per 2 stations = 3 total)
2ndSem.-Physics
Light and Optics - Instructor
Lab #LO4 - Equipment
LO-Lab#04
2ndSem.-Physics
Light and Optics - Instructor
Prepared Sample Solutions
LO-Lab#04
2ndSem.-Physics
Light and Optics - Instructor
LO-Lab#04
Big Ideas
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This lab introduces the use of a colorimeter.
It also gives students the opportunity to apply concepts related to optical density
(absorbance), transmission, and the effect of different colors of filters with different
colors of light.
General Information on the Sample Solutions
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Students will be studying sample solutions of a "child's cough medicine." It is actually
water with red food coloring and should pose no hazard to anyone.
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Known concentrations of the following values (mg/L) will be provided: 0, 1, 2, 3, 4, 7,
10, and 13. There will also be the unknown sample.
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Sample sets are located in three places around the room so students don't have to crowd
around one location. Students should be careful with these samples as they will be used
by all lab sections.
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There is also a 2-L pop bottle with some of the unknown sample on the front desk.
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If disaster strikes and a sample is spilled or otherwise contaminated, there are extra
samples stored on the table in Ferguson 316.
Experimental Hints and Procedures
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Task #1 – 1: Students should pick which color of light to use. You should not tell them
or advise them on this decision. Even after last week's lab, many will still want to start
with red light to studying the absorption of the red solution. Even though their data
won't be very interesting and they may decide to switch, they will learn a lot about
absorption! That's the whole point! They won't learn this unless they try it out.
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Task #1 – 2: All groups should use blue or green light at this point.
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All used samples should be discarded into the plastic tubs. This will keep the original
samples from being contaminated.
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Students should work together in their groups to solve the Application Activity. You
can offer guiding questions and hints, but you should not solve it for them.
Application solution
The accident most likely occured about 7.5 hours ago plus or minus a half an hour.
% transmission
9
10
8
OD
1.046
OD-.3
0.746
1.000
1.097
hours since accident
7.46
0.700
0.797
7.00
7.97
2ndSem.-Physics
Light and Optics - Instructor
LO-Lab#04
Sharing Data
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Students should record their results on a white board. They will need this information
for the concluding questions. You might construct a table for them to fill in such as the
following. You might also record this information on the back page so you will have it
when you go to grade.
Light Color
Mathematical Model
Concentration of
Unknown
Cleanup:
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Be sure that all cuvettes have been emptied and rinsed with clear water. They should be left
uncapped so they can dry out.
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Return all sample containers to the equipment tables/storage carts.
2ndSem.-Physics
Light and Optics - Instructor
LO-Lab#04