Chapter 26: Optoelectric Devices
MULTIPLE CHOICE
1. The ____ is the oldest optoelectric device. It is a light-sensitive device in which the internal resistance
changes with a change in light intensity.
a.
photodiode
c.
photo cell
b.
solar cell
d.
light-emitting diode
2. The ____ is more sensitive to light than any other device.
a.
photo cell
c.
photodiode
b.
solar cell
d.
phototransistor
3. ____ are used in light meters for photographic equipment, instruction detectors, automatic door
openers, and various kinds of test equipment to measure light intensity.
a.
Light-emitting diodes
c.
Photodiodes
b.
Solar cells
d.
Photo cells
4. The ____ is a highly inefficient device, with a top efficiency of 15 to 20%, in terms of electrical power
output compared to the total power contained in the input light energy.
a.
photodiode
c.
phototransistor
b.
solar cell
d.
photo cell
5. ____ have a low voltage output of about 0.45 volt at 50 milliamperes and must be connected in a series
and parallel network to obtain the desired voltage and current output.
a.
Solar cells
c.
Photodiodes
b.
Phototransistors
d.
Light-emitting diodes
6. Applications of ____ include light meters for photographic equipment, motion-picture projector
soundtrack decoders, and battery chargers on satellites.
a.
photodiodes
c.
light-emitting diodes
b.
phototransistors
d.
solar cells
7. The advantage of the ____ is fast response to light changes, the fastest of any photosensitive device.
a.
photodiode
c.
phototransistor
b.
solar cell
d.
photo cell
8. Applications of the ____ include phototachometers, photographic exposure controls, flame detectors,
object counters, and mechanical positioners.
a.
photo cell
c.
solar cell
b.
phototransistor
d.
photo diode
9. The ____, being a semiconductor component, has an unlimited life span due to the absence of a
filament, a cause of trouble in conventional lamps.
a.
solar cell
c.
light-emitting diode
b.
photodiode
d.
photo cell
10. An LED used in conjunction with a ____ forms an optical coupler.
a.
photo cell
c.
solar cell
b.
photodiode
d.
phototransistor
COMPLETION
1. ____________________ is electromagnetic radiation that is visible to the human eye.
2. ____________________ are constructed in two ways. One method is as a simple PN junction. The
other method inserts an intrinsic (undoped) layer between the P and N region.
3. A(n) ____________________ is used like a photodiode and packaged like a photodiode, except that it
has three leads (emitter, base, and collector).
SHORT ANSWER
1. What is a photoconductive cell (photo cell)?
2. How does a PN junction photodiode operate?
