QUES: Many sensor systems rely on light as the signal source. LEDs are often ideal as a light source due to the requirements of the sensors. LEDs are used as motion sensors, for example in optical computer mice. The Nintendo Wii's sensor bar uses infrared LEDs. Pulse oximeters use them for measuring oxygen saturation. Some flatbed scanners use arrays of RGB LEDs rather than the typical cold-cathode fluorescent lamp as the light source. Having independent control of three illuminated colors allows the scanner to calibrate itself for more accurate color balance, and there is no need for warm-up. Further, its sensors only need be monochromatic, since at any one time the page being scanned is only lit by one color of light. Since LEDs can also be used as photodiodes, they can be used for both photo emission and detection. This could be used, for example, in a touchscreen that registers reflected light from a finger or stylus. Many materials and biological systems are sensitive to, or dependent on, light. Grow lights use LEDs to increase photosynthesis in plants, and bacteria and viruses can be removed from water and other substances using UV LEDs for sterilization.

non- What device uses infrared LEDs to measure oxygen saturation?
What is the answer?
ANS: unanswerable
QUES: Although theoretically a collegial body operating through consensus building, Gaddafi dominated the RCC, although some of the others attempted to constrain what they saw as his excesses. Gaddafi remained the government's public face, with the identities of the other RCC members only being publicly revealed on 10 January 1970. All young men from (typically rural) working and middle-class backgrounds, none had university degrees; in this way they were distinct from the wealthy, highly educated conservatives who previously governed the country.

What was the sex of all the members of the RCC?
What is the answer?
ANS: men
QUES: The Slavs under name of the Antes and the Sclaveni make their first appearance in Byzantine records in the early 6th century. Byzantine historiographers under Justinian I (527565), such as Procopius of Caesarea, Jordanes and Theophylact Simocatta describe tribes of these names emerging from the area of the Carpathian Mountains, the lower Danube and the Black Sea, invading the Danubian provinces of the Eastern Empire.

Tribes of Slavs were invading what provinces of the Eastern Empire?
What is the answer?
ANS:
the Danubian provinces