NCERT Class 7 Geography — Chapter 1: Water

The correct option is

Full Moon and New Moon

Explanation

Tides are the periodic rise and fall of sea levels caused principally by the gravitational forces exerted by the Moon and the Sun, combined with the rotation of the Earth. The magnitude of the tidal range (the difference between high and low tide) fluctuates based on the relative alignment of the Earth, Moon, and Sun.

Detailed Analysis

• Spring Tides: These tides occur when the Sun, Moon, and Earth are aligned in a straight line. This configuration is known as syzygy.
  • During a New Moon, the Moon and Sun are on the same side of the Earth, and their gravitational forces combine to pull the ocean water in the same direction.
  • During a Full Moon, the Moon and Sun are on opposite sides of the Earth, but their gravitational pulls still reinforce each other along the same axis.
  In both cases, the combined gravitational force is at its strongest, resulting in the highest high tides and the lowest low tides. Thus, Spring Tides occur twice a month during the Full Moon and New Moon.
• Neap Tides: These occur when the Sun and Moon are at right angles to each other relative to the Earth (quadrature). This happens during the First Quarter and Last Quarter phases. In this position, the gravitational force of the Sun partially counteracts that of the Moon, resulting in lower high tides and higher low tides (minimum tidal range).

Key Takeaway: Spring tides occur during syzygy (Full Moon and New Moon) and exhibit the maximum tidal range, whereas Neap tides occur during quadrature (First and Last Quarter) and exhibit the minimum tidal range.