Geographical knowledge about high school geography, terminator line problem and so on

1. The time for the meridian to cross the morning line and the equator is 6 o'clock, and the time for the meridian to cross the dark line and the equator is 18 o'clock. (the same place on the same longitude line is the same) remember accurately,

2, your second question should actually be one, that is, to find the latitude of the direct point of the sun according to the height of the sun, and the local latitude you said is also the latitude of the direct point, so I will answer it according to this meaning.

At noon at a certain latitude, the height of the sun h = 90°- the latitude difference between the local latitude and the direct point (latitude interval).

The local latitude in the formula is the latitude of the place you want.

To give a few examples: (1) It is known that the direct sunlight is 20 N, and the noon sun height in a certain place is 50 N ... where 50 N is the local latitude.

The method is: H = 90-(50-20) = 60.

(2) It is known that the direct sunlight is 20 N, and the noon sun height in a certain place is10 N..

The method is: H = 90-(20- 10) = 80.

(3) It is known that the direct sunlight is 20 N, and the noon sun height of a place of 30 s is calculated.

The method is: H = 90-(20+30) = 40.

Among the three problems, the key is to understand the meaning of latitude difference.

On the other hand, if you know the noon sun height of a place and find the local latitude, you must know the latitude of the direct point of the sun to find it. In other words, there are three unknowns in the above formula. As long as you know any two, you can find the third one. I won't give examples.

3. About the shadow length. Generally, the change of shadow length and the calculation of shadow length are investigated at two points.

(1) There are two changes in the length of the shadow: daily change and annual change.

Diurnal variation: In a day, the shadow of an object is shortest at noon and longest at sunrise and sunset (theoretically infinite).

Therefore, the shadow length becomes shorter from sunrise to noon and longer from noon to sunset.

In a year, the shadow length of an object is the shortest in the local summer solstice and the longest in the local winter solstice.

The diurnal variation mainly considers the diurnal variation of solar height, and the annual variation mainly considers the annual variation of solar height at noon.

(2) The calculation of shadow length is mainly based on trigonometric function, which is not easy to express in words. If you really meet me, I will tell you.

I hope you can understand and wish you success in your studies.