The angle calculated by these latitudes is theoretically the direct angle at noon, not the oblique angle in the morning. The actual error is not big, so we won't talk about it. Around the summer solstice, the sun can enter the house in the morning and will not enter until after the autumnal equinox (the specific time is not counted). Before the vernal equinox of the new year, winter is even more impossible without the sun.
As shown in the figure:
Extended data:
It is the degree to which the object is illuminated, that is, the ratio of the luminous flux obtained on the surface of the object to the illuminated area. The unit is Ix(l lux is the illuminance generated by the luminous flux of L lumens uniformly illuminating an area of L square meters) or foot candle.
(1 foot candle is the illuminance generated by 1 lumen luminous flux uniformly illuminating 1 square foot area), 1 foot candle =10.71x. Illuminator for measuring light intensity.
In summer, under direct sunlight, the light intensity can reach 60000 ~ 65438+1000000lx, and there is no sun outside.10000 ~100000lx, and it is sunny indoors in summer100 ~ 550/kloc-0.
Incandescent lamps can emit about 12.56 1x per watt, but the value varies with the size of the bulb. Small bulbs can emit more lumens, while large bulbs emit less. The luminous efficiency of fluorescent lamps is 3 ~ 4 times that of incandescent lamps. Life expectancy is 9 times that of incandescent lamps, but the price is higher, but it is just the light emitted by incandescent bulbs without lampshades.
About 30% of lumens are absorbed by walls, ceilings, equipment, etc. The poor quality of light bulbs and dim light will reduce many lumens, so only about 50% lumens can be used. Generally, when there is a lampshade and the height of lamps is 2.0~2.4m (the distance between bulbs is 1.5 times the height).
LW bulbs or 1m2 are required for every 0.37m2 area, and 2.7W bulbs are required for this area to provide10.71x. The installation height of the bulb and the existence of the lampshade have great influence on the light intensity (table 1).
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