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cell is 125 volts, the caesium is about 90 volts. The caesium cell will ionize on anything above 90 volts. Caesium cells should never be exposed to bright sunlight as this may ruin the sensitivity of the cell.
Due to the high gain of a caesium cell, it is possible to eliminate one stage of amplification in the projector system, although this is not the general practice. The caesium cell can be coupled with a transformer to the amplifier, while the potassium must be resistance coupled for best results. The usual method of using a caesium cell is to cut down on the attenuator or insert a loss pad until the proper level is obtained. By doing this the machine noise and other noises are greatly reduced.
In the illustration we have a graph plotting the response per unit of energy against the wave length of light in Angstrom units. By looking at the potassium curve, we find that its response is high in the ultra violet zone, and drops off in the violet and red zone to nothing at about 6400 Angstrom units. The caesium curve is very high in the ultra violet zone, then it drops in the violet and red zone to rise again in the end of the red and infra red zone, which is about 8000 Angstrom units. The zone between 3800 and 8000 Angstrom units is the limit of visabilfty that is the zone of color perceptible to the eye. The zone between 2400 and 8000 Angstrom units constitutes the wave length of white light.
Questions and Answers
Q. Why can’t dry batteries be charged the same as storage batteries?
A. The chemical action that takes place in a storage battery is said to be reversible, that is, a certain chemical action occurs when current is taken from the battery, by reversing the current through the battery this action can also be reversed and the battery is changed so that it again is the same as it was before the discharge took place.
In the dry battery this is impossible. When current is taken from a dry battery the zinc is decomposed ; and it is not possible to take the products of this decomposition and again produce zinc by putting a current through the battery in the reverse direction.
Q. Why is the sound printed 14 inches ahead of the picture on the movietone film?
A. Probably a correct answer would be that sound is printed 14 inches ahead of the picture because the movietone pick-up is located that far below the picture aperture.
No doubt what you have in mind is why don’t they put the pick-up in the same position that the aperture is, then the sound and picture could be printed at the same place instead of staggering them.
One of the most important things about film reproduction is that the film move at a steady, uniform speed, otherwise the sound will waver or flutter. Since the film moves intermittently at the aperture it is obvious that it cannot be made to also move steadily, so movietone pick-up at this point is impossible.
McBride: I have invented a ma
chine that will do the work of 10 men. It ought to help the unemployment situation.
Haskell: How come?
McBride: It takes 15 men to
run it.
T h i r ty -seven