This final article in the series on the fine-beam cathode-ray tube presents: (1) additional investigations; (2) an alternative method for the electron e/m and synchrotron radiation; and (3) two challenges to students (in a dialogue format) together with a lengthy discussion on synchrotron radiation sources. (DH)

Presents (in the form of a dialogue between a student and teacher) an alternative method of using the Fine-Beam Cathode-Ray Tube to obtain the value for the specific electronic charge e/m. (JN)

Examines (in the form of a hypothetical dialog between a teacher and a student) the nature of the mantle and the spectral content of the glow which lights up both beam and mantle. These phenomena are associated with excitation of helium gas in the presence of electromagnetic and electrostatic fields. (JN)

Discusses use of a tangential gun to obtain a value for the specific electronic charge e/m. The method is the one advocated by the tube suppliers, though some suggested variations may appeal to teachers anxious to train their students in thinking along lines that are both scientifically correct and practically desirable. (JN)

Discusses the physics of electromagnetic focussing using an imaginary dialogue between teacher and student. It is assumed that students have been introduced to the underlying theory concerning movement of a charged particle traveling with uniform speed in a magnetic field before seeing a demonstration with the fine-beam cathode-ray tube. (JN)

Discusses use of the fine-beam cathode-ray tube to investigate strength and direction of the earth's magnetic field, simulating discussion between student and teacher as the equipment is set up and the experiment done. Provides diagrams and illustrative photographs to aid in equipment set-up and measurement. (JM)

Describes (in the form of a hypothetical discussion between teacher and student) several demonstrations using the fine-beam cathode-ray tube. One is a demonstration of how a magnetic field can help to initiate and propagate a fine beam. (JN)