Minimum sunshine area of sunshine room in Taiyuan area.

Midday in summer. When the height angle of the sun is the largest, the sunshine area shining into Taiyuan's houses is the smallest, that is, in the afternoon of summer solstice in the north. On the day of summer solstice, the position where the sun shines directly on the ground reaches the northernmost part of the year, almost directly on the tropic of cancer. At this time, the daylight hours in all parts of the northern hemisphere reach the longest in the whole year.