Final answer:
Diurnal tides with a period of 24 hours and 50 minutes are explained by the Earth's rotation under the tidal bulges caused by the Moon's gravitational pull, combined with the Moon's own orbit around the Earth, which extends the tidal period slightly beyond a standard 24-hour solar day.
Step-by-step explanation:
Regarding diurnal tides, which have one high and one low tide each day with a period of about 24 hours and 50 minutes, it is important to understand the dynamic interplay of the Earth's rotation, the Moon's gravitational pull, and the relative motion of the Moon in its orbit around the Earth.
While Equilibrium Theory of Tides explains that there are two tidal bulges on Earth due to the Moon's gravitational pull, one on the side closest to the Moon and one on the opposite side, it does not account for the Earth's rotation or the Moon's orbit thoroughly. As the Earth rotates (taking approximately 24 hours for a full rotation), it moves underneath these bulges. Due to this rotation, an observer would experience a high tide when their location passes under one of the bulges. However, since the Moon also orbits Earth approximately every 28 days in the same direction of the Earth's rotation, the bulges are not stationary. Consequently, the time between the high tides is not precisely 12 hours but rather about 12 hours and 25 minutes.
This slight discrepancy accumulates over a lunar day (the time it takes for a point on Earth to make one full rotation in respect to the Moon), which is 24 hours and 50 minutes, not the standard 24-hour solar day. This is why diurnal tides with a period of 24 hours and 50 minutes exist—one rotation of Earth does not align perfectly with the timing of the tidal forces due to the Moon's orbit, creating the observed lag.