Which of the following occurs when the sun is vertically overhead at the equator?

Step 1: Analyze the question The question asks what happens when the sun is directly overhead (at 90°) at the equator (0° latitude).

Step 2: Explain the concept The sun's vertical rays move between the Tropic of Cancer (23½°N) and the Tropic of Capricorn (23½°S) during the year, as the Earth revolves around the sun on its tilted axis.

• Equinox: the sun is vertically overhead at the equator. This happens around 21 March (March equinox) and 23 September (September equinox). Day and night are about equal (12 hours each) everywhere.
• Solstice: the sun is vertically overhead at one of the tropics. This happens around 21 June (Tropic of Cancer) and 22 December (Tropic of Capricorn).

Step 3: Check each option

• A. Equinox: correct. This is the definition above.
• B. Solstice: wrong. The sun is overhead at the tropics, not the equator.
• C. Deflection of winds and ocean currents: this is caused by the Earth's rotation (the Coriolis effect), not by the sun's position.
• D. Rise and fall of tides: this is caused mainly by the gravitational pull of the moon (and the sun), not by the sun being overhead at the equator.

Step 4: Answer The correct answer is A. equinox.

Exam tip: Remember: "Equinox = Equator". Both start with "E". Solstice means the sun reaches its farthest point north or south, over the Tropics of Cancer or Capricorn.