The direct rays of the sun apparently travel 23.5 degrees of latitude north from path d to path a during the Northern Hemisphere summer solstice.
The apparent movement of the sun's direct rays across the Earth's surface is influenced by the tilt of the Earth's axis. During the Northern Hemisphere summer solstice, which occurs around June 21st, the North Pole is tilted towards the sun. This tilt causes the sun's rays to appear directly overhead at the Tropic of Cancer, approximately 23.5 degrees north latitude.As a result, the sun's direct rays seemingly travel 23.5 degrees of latitude northward from a more southern path, such as path d, to reach the Tropic of Cancer or path a. This phenomenon is a key factor in the changing seasons and the variation in daylight hours experienced at different latitudes throughout the year.