Cheat Sheet
LDR ms Optical detector
Optical source Forward-biased photodiode; energy releases photo of light (near-infrared) -Resistance against light -High gain means slower -Limiting resistor is used to keep the intensity is plotted on a log-log response time current within the maximum allowed scale -More sensitive than a rating. - When it’s darker, it will have a photodiode (can pick up smaller -The brightness of the LED depends higher resistance. If it has a changes in light) on the current, and NOT the voltage higher resistance, then it will -Slower response times than (since the voltage doesn’t surpass the = = have more voltage. photodiodes (lower bandwidth) switch-on voltage) -In reverse-biased, movement -Cheap and easy to build - The base current is generated - Emits light of different wavelengths is the photocurrent -Resistance depends on the by the light absorbed. depending on the semiconductor (photoconductive mode) amount of light shining on it material it is made from Photonics is the science of using light to manipulate information and energy where light Current, (1A = 1Cs-1; 1C = As): = is modelled as a stream of photons, each with a quantum (packet) of energy; Voltage (potential difference), (1V = 1JC-1): = where = The photophone; Problems: Light sources (sun or lantern) weren’t bright enough (lasers -1 invented) and “line of sight” air path was unstable due to fog or rain (glass optical fibres Resistance, (1 Ω = VA ): If there is more resistance through a branch of a parallel circuit, then there is less current flowing through that branch. In series, a higher developed) resistance will cause more voltage to be dissipated across it. The information-carrying capacity of any telecommunications system is determined by Resistivity: a measure of the the highest frequency that can be practically sent (bandwidth, Hz). Series Parallel inherent resistance of the material When sending a DC current, electrons will travel all throughout the wire. However, V = = = 2= 2
Optical source Forward-biased photodiode; energy releases photo of light (near-infrared) -Resistance against light -High gain means slower -Limiting resistor is used to keep the intensity is plotted on a log-log response time current within the maximum allowed scale -More sensitive than a rating. - When it’s darker, it will have a photodiode (can pick up smaller -The brightness of the LED depends higher resistance. If it has a changes in light) on the current, and NOT the voltage higher resistance, then it will -Slower response times than (since the voltage doesn’t surpass the = = have more voltage. photodiodes (lower bandwidth) switch-on voltage) -In reverse-biased, movement -Cheap and easy to build - The base current is generated - Emits light of different wavelengths is the photocurrent -Resistance depends on the by the light absorbed. depending on the semiconductor (photoconductive mode) amount of light shining on it material it is made from Photonics is the science of using light to manipulate information and energy where light Current, (1A = 1Cs-1; 1C = As): = is modelled as a stream of photons, each with a quantum (packet) of energy; Voltage (potential difference), (1V = 1JC-1): = where = The photophone; Problems: Light sources (sun or lantern) weren’t bright enough (lasers -1 invented) and “line of sight” air path was unstable due to fog or rain (glass optical fibres Resistance, (1 Ω = VA ): If there is more resistance through a branch of a parallel circuit, then there is less current flowing through that branch. In series, a higher developed) resistance will cause more voltage to be dissipated across it. The information-carrying capacity of any telecommunications system is determined by Resistivity: a measure of the the highest frequency that can be practically sent (bandwidth, Hz). Series Parallel inherent resistance of the material When sending a DC current, electrons will travel all throughout the wire. However, V = = = 2= 2