On July 1, 2020, this post will be obsolete. See the corresponding post from my 2020 version of No Nonsense Extra Class License Study Guide.
Two questions—E6F13 and E6F14—about LCD displays were added to this section. The other questions were unchanged…Dan
E6F: Optical components: photoconductive principles and effects, photovoltaic systems, optical couplers, optical sensors, and optoisolators; LCDs
The photovoltaic effect is the conversion of light to electrical energy. (E6F04) In a photovoltaic cell, electrons absorb the energy from light falling on a photovoltaic cell. (E6F12) The electrons then become free electrons.
The most common type of photovoltaic cell used for electrical power generation is silicon. (E6F10) The approximate open-circuit voltage produced by a fully-illuminated silicon photovoltaic cell is 0.5 V. (E6F11) The efficiency of a photovoltaic cell is the relative fraction of light that is converted to current. (E6F09)
Photoconductivity is a similar phenomenon. Photoconductivity is the increased conductivity of an illuminated semiconductor. (E6F01) The conductivity of a photoconductive material increases when light shines on it. (E6F02) A crystalline semiconductor is the material that is affected the most by photoconductivity. (E6F06)
A device that uses the phenomenon of photoconductivity is the optoisolator. The most common configuration of an optoisolator or optocoupler is an LED and a phototransistor. (E6F03) Optoisolators are often used in conjunction with solid state circuits when switching 120 VAC because optoisolators provide a very high degree of electrical isolation between a control circuit and the circuit being switched. (E6F08)
A similar device is the solid-state relay. A solid state relay is a device that uses semiconductor devices to implement the functions of an electromechanical relay. (E6F07)
Optical shaft encoders are another device that rely on photoconductivity. An optical shaft encoder is a device which detects rotation of a control by interrupting a light source with a patterned wheel. (E6F05) Optical shaft encoders are used to detect when an operator turns a knob on an amateur radio transceiver.
Liquid crystal displays
A liquid crystal display (LCD) is a display utilizing a crystalline liquid and polarizing filters which becomes opaque when voltage is applied. (E6F13) One thing that is true of LCD displays is that they may be hard to view through polarized lenses. (E6F14)
Bob, KG6AF says
FYI – The NCVEC has just withdrawn the 2016 Extra Class question pool, and will replace it with a new one on a date not yet specified.
http://www.ncvec.org/page.php?id=366
Dan KB6NU says
Yeah. Someone posted that info to the ham_instructor mailing list.
I’m a little miffed about this. I understand that this is all volunteer work, but even so, I think the NCVEC and the Question Pool Committee needs to tighten up their process a little. So I don’t sound like a big complainer, I’ve volunteered to help the QPC in the future.