Questions 31-33 refer to the following apparatus used to study the photoelectric effect.
In this apparatus, the photocathode and the collector are made from the same material. The potential V of the collector, measured relative to ground, is initially zero and is then increased or decreased monotonically. The effect is described by Einstein’s photoelectric equation: |eV| = hv − W
When the photoelectric equation is satisfied and applicable to this situation, V is the
A. Negative value at which the current stops
B. Negative value at which the current starts
C. Positive value at which the current stops
D. Positive value at which the current starts
E. Voltage induced when the light is on
(GR8677 #31)
Solution:
Stopping potential, V:
- The point at which no electrons make it to the collector.
- The electron charge is negative and the potential V must be a negative quantity in order to make eV positive overall.
- It is related to the maximum kinetic energy of the ejected electrons by eV = KEmax = ½ m (vmax)²
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