No, the sun comes out approximately 1.5° from east to south, and sets at 1.5° from west to south (not northwest). Similarly, the vernal and autumnal equinoxes are 25° (that is, directly hitting the equator, the height of the sun is the latitude. According to Kunming’s latitude of 25°), the winter solstice reaches a position of 48.5° east to south.

The angle calculated by these latitudes is theoretically the direct angle at noon, not the oblique angle in the morning. However, the actual calculation error is not big, so we can just forget it. Sunlight can enter the house before and after the summer solstice in the morning, but not until after the autumnal equinox (the specific time is not counted), and before the spring equinox in the new year, no sun can enter, and it is even less possible in winter.

As shown in the figure:

Extended information:

It is the degree to which an 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 illumination produced by a luminous flux of l lumen evenly irradiating an area of ??l square meters) or footcandle.

(1 foot candle is the illumination produced by 1 lumen of luminous flux uniformly illuminating an area of ??1 square foot), 1 foot candle = 10.761x. Light intensity is measured with a light meter.

Under direct sunlight in summer, the light intensity can reach 60,000-100,000 lx, 01,000-10,000 lx outdoors without sunlight, 100-5501x indoors in bright summer, and 0.21x under the full moon at night. .

Incandescent lamps can emit approximately 12.561x light per watt, but the value varies with the size of the bulb. Small bulbs can emit more lumens, while large bulbs can emit less. The luminous efficiency of fluorescent lamps is 3 times that of incandescent lamps. ~4 times. The lifespan is 9 times that of incandescent lamps, but the price is higher. But in the light emitted by an incandescent bulb without a lampshade.

About 30% of the lumens are absorbed by walls, ceilings, equipment, etc.; the poor quality and darkness of the light bulbs reduce a lot of lumens, so only about 50% of the lumens are available. Generally, when there is a lampshade and the lamp height is 2.0~2.4m (the distance between the bulbs is 1.5 times the height).

Every 0.37m2 area requires lW bulbs or 1m2, and the area requires 2.7W bulbs to provide 10.761x. The height of the bulb installation and the presence or absence of a lampshade have a great influence on the light intensity (Table 1).

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