Download Giessler/Crookes Tube and Cathode Ray

This is very good, se my comments and delete/move/reword things.
Please do not make copies until we agree on the details.
Eugenia
Giessler/Crookes Tube and Cathode Ray Activity This is not an observation activity, this is
the whole cycle, right?
Delete the underlined, you need to start from observations, this statement should be later, after
observations are done, nobody knew about the rays until the first experiments, right?
Directions: How will they know what cathode rays are? You need to start with the observations
of the glass tubes that led to the idea of the rays. You need to delete the first sentence and only
leve the last one, in bold now. Record all observations for each experiment and reason
through a possible explanation for the phenomena observed in the tubes. Do you mean
come up with explanations? Drawing conclusion is not a scientific term.about the nature of
the cathode rays. Delete the underlined.
Experiment #1
This observational experiment was made in a bent Giessler tube. The lower case “g” is where
the most intense phosphorescence occurs. The intense area of phosphorescence is located
directly across the cathode of the Giessler tubes. In the picture below, What are they going to
see here? May be you need to describe some of the observations that were made without using
the words cathode rays at all.
(insert pic)
Experiment #2
This observational experiment is made in a Giessler tube with a Maltese cross in the middle of
the tube. The picture below shows what is made after the cathode rays hit the cross and the back
of the Giessler tube. What are the possible explanations for what was observed?
If possible conduct the simulation online here
http://micro.magnet.fsu.edu/electromag/java/crookestube/
Or examine the pictures below.
What kind of an experiment is it? Observational or testing? Specify. Testing Experiment #3
Utilizing the information from Experiments #1 and #2 make a prediction about the nature of the
phenomena observed in experiment #1 and #2. Examine the phenomena’s interaction with a
magnet. Observe what happens to the phenomena when a bar magnet is placed near it. This was
probably already a testing experiment because they were thinking of what the rays could be, so
you need to have students come up with the explanations and they decide how they can test
them, ok?
Bar Magnet
S
N
S
Examine the magnetic field produced by a bar magnet. What does this information tell us about
the magnetic field entering the cathode’s path?
S
N
Testing Experiment #4
Predict what will happen as a magnetic field approach an electromagnetic wave. Examine the
interactions of electromagnetic waves and magnetic fields. Observe what happens when a
magnet is placed near the path of a laser pointer. Does this experiment disprove or prove
anything about the prediction in experiment #3? Revise or restate your prediction if necessary
from Experiment #3.
Testing Experiment #5
Predict what will happen to the phenomena when it enters an electric field. For this particular
device, when the DC voltage is set to - 50 V the bottom plates are positively charged and the
upper plates are negatively charged. Examine the cathode rays interactions with an electric field.
Adjust the potential difference between the parallel plates on the cathode rays. Observe what
happens as the potential changes as the rays pass through the plates. How do these observations
compare with your predictions?
Conclusion
How can you explain what cathode rays are? Are these cathode rays light? Justify why/why
not?