Consider the following statements: 1. The vernal equinox falls on March 21. 2. On equinox, the sun is directly overhead at the equator. 3. The changes in the day length on equinox result from the changes in the tilt of the earth with respect to the sun. Which of the statements given above is/are correct?

Statement 1 is correct as the vernal (spring) equinox typically falls on March 21, marking the start of spring in the Northern Hemisphere [3]. While the date can vary between March 20 and 21 due to the leap year cycle, March 21 is a standard astronomical reference [6]. Statement 2 is correct because during an equinox, the Sun's declination is 0°, meaning it is directly overhead at the equator at noon [t1][t2]. Statement 3 is incorrect; the equinox itself is the moment when the Earth's axial tilt is neither toward nor away from the Sun [t4][t6]. The changes in day length throughout the year are caused by the constant 23.5° axial tilt combined with Earth's orbital motion, but on the equinox specifically, the tilt is perpendicular to the Sun's rays, resulting in nearly equal day and night globally [c2][t7].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 19: The Motions of The Earth and Their Effects > Equinox > p. 254
2. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 12: Major Crops and Cropping Patterns in India > Biotic: Living > p. 126
3. [2] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > THE ALTITUDE OF THE MIDDAY SUN > p. 7
4. [6] https://www.nesdis.noaa.gov/news/earth-orbit-vernal-equinox