During sunset, why do mountaintops still get sunlight after the sun isn't visible from the ground?

The sun is below the horizon, but its rays are scattered by Earth's atmosphere to create the colors of twilight. We have twilight because Earth has an atmosphere. Some light scatters through small particles in the atmosphere – so there's still some light in the sky even after the sun has gone down.This time of day is important for a lot of reasons to many people – for example, astronomers, who are waiting for true darkness to fall so they can begin their observations. So some more strict definitions have evolved on the subject of twilight.

That's a BEAUTIFUL photo.  I'd like to know where it came from.

The answer to the question is:  

For the same reason that you can see farther when you're higher.  Because the Earth is round, a sphere, the shape of a ball.

This beautiful photo is the answer to anyone who claims that the Earth is flat.  It totally debunks every possible weird and twisted explanation they can come up with. This picture can't happen on a flat Earth, no matter what you try to do with density, buoyancy, perspective, refraction, sheep, holograms, indoctrination, cognitive dissonance, or NASA.

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: