Final answer:
The latitude at which the highest amount of solar radiation reaches the surface of the Earth is the Tropic of Cancer at approximately 23° N latitude.
Step-by-step explanation:
The latitude at which the highest amount of solar radiation reaches the surface of the Earth is the Tropic of Cancer, which is at approximately 23° N latitude. This latitude experiences the Sun being directly overhead at noon on the first day of summer, also known as the summer solstice.
The Sun's rays shine down most directly upon the Northern Hemisphere at this latitude.