When the solar altitude is at 90 degrees, what latitude on the Earth's surface is this known as?

• A. Prime Meridian
• B. Equator
• C. Declination of the Sun
• D. North Pole

Answer: (C)

When the solar altitude is at 90 degrees, it indicates that the Sun is directly overhead at that specific latitude. This phenomenon occurs at the equator. The latitude corresponding to a solar altitude of 90 degrees is known as the equator, which is located at 0 degrees latitude.

The term "declination of the Sun" refers to the angle between the rays of the sun and the plane of the Earth's equator, which changes throughout the year as the Earth orbits the Sun. Understanding this concept is critical in determining the latitude at which the Sun's rays strike directly overhead, which happens at the equator during the equinoxes.

Therefore, when identifying the latitude where the Sun is at its zenith (90 degrees), the equator is the correct reference point.