Question: An important property of light fixtures is the luminous efficacy or wall-plug efficiency, meaning the amount of usable light emanating from the fixture per used energy, usually measured in lumen per watt. A fixture using replaceable light sources can also have its efficiency quoted as the percentage of light passed from the "bulb" to the surroundings. The more transparent the lighting fixture is, the higher efficacy. Shading the light will normally decrease efficacy but increase the directionality and the visual comfort probability.
Try to answer this question if possible: Luminous efficacy is measure in what unit?
Answer: lumen per watt
Question: From roughly 115 to 60 BC, Han forces fought the Xiongnu over control of the oasis city-states in the Tarim Basin. Han was eventually victorious and established the Protectorate of the Western Regions in 60 BC, which dealt with the region's defense and foreign affairs. The Han also expanded southward. The naval conquest of Nanyue in 111 BC expanded the Han realm into what are now modern Guangdong, Guangxi, and northern Vietnam. Yunnan was brought into the Han realm with the conquest of the Dian Kingdom in 109 BC, followed by parts of the Korean Peninsula with the colonial establishments of Xuantu Commandery and Lelang Commandery in 108 BC. In China's first known nationwide census taken in 2 AD, the population was registered as having 57,671,400 individuals in 12,366,470 households.
Try to answer this question if possible: When was the first national census taken in China?
Answer: 2 AD
Question: The current "Precentor" (Head of Music) is Tim Johnson, and the School boasts eight organs and an entire building for music (performance spaces include the School Hall, the Farrer Theatre and two halls dedicated to music, the Parry Hall and the Concert Hall). Many instruments are taught, including obscure ones such as the didgeridoo. The School participates in many national competitions; many pupils are part of the National Youth Orchestra, and the School gives scholarships for dedicated and talented musicians. A former Precentor of the college, Ralph Allwood set up and organised Eton Choral Courses, which run at the School every summer.
Try to answer this question if possible: How many organs does Eton house?
Answer: eight
Question: The earliest examples of visual representations in Iranian history are traced back to the bas-reliefs of Persepolis, c. 500 BC. Persepolis was the ritual center of the ancient kingdom of Achaemenids, and the figures at Persepolis remain bound by the rules of grammar and syntax of visual language. The Iranian visual arts reached a pinnacle by the Sassanid Era. A bas-relief from this period in Taq Bostan depicts a complex hunting scene. Similar works from the period have been found to articulate movements and actions in a highly sophisticated manner. It is even possible to see a progenitor of the cinema close-up in one of these works of art, which shows a wounded wild pig escaping from the hunting ground.
Try to answer this question if possible: How far back can the first known examples of Iranian visual art be traced to?
Answer:
c. 500 BC