(i) While revolving around the earth, the moon makes a right angle with respect to the earth and the sun, twice a month.
(ii) This position occurs on the first and third quarter of each month. On both these days the forces of both the sun & the moon operate at right angles on the earth.
(iii) At the places where the sun causes high tide, the gravitational pull of the moon which is at right angles also acts on the water.
(iv) Due to such conditions the water level rise is less than usual at the time of high tide. Similarly, fall in water level is less than usual at the time of low tide.
(v) Such tides are called neap tides.
