Question

Do the vertical rays of the sun migrate between 23.5 degrees N and 23.5 degrees S?

Answer 1

yes the sun is directly overheat at summer solstice at the Tropic of Cancer (23.5oN). This is as the most northernly latitude which has the sun directly overheat at any time of year. A similar case happen at winter solstice at Tropic of Capricorn (23.5oS)