Tides (ज्वार-भाटा)
The rise in the sea level due to the attractive force of the Sun and the Moon is called tide (ज्वार), and the fall in the sea level is called ebb (भाटा).
The ratio of the attractive force of the Sun and the Moon is 5:11.
The attractive force of the Moon is 2.17 times greater than the attractive force of the Sun.
Generally, a place experiences two tides and two ebbs in one day.
One tide is caused by the Moon's attractive force, and one is caused by the centrifugal force.
The next tide comes with a delay of 26 minutes after the previous one.
Reason: Due to the Moon's revolution around the Earth.
The ebb comes 6 hours and 13 minutes after the tide.
The tide caused by the Moon's attractive force is called the Direct Tide (प्रत्यक्ष ज्वार), and the tide caused by the centrifugal force is called the Indirect Tide (अप्रत्यक्ष ज्वार).
High Spring Tide (दीर्घ ज्वार)
When the Sun, Moon, and Earth are all in a straight line (syzygy), the resulting tide is about 20 percent higher than a normal tide.
High spring tides always occur on the Full Moon (पूर्णिमा) and New Moon (अमावस्या).
Low Neap Tide (लघु ज्वार)
When the Sun, Moon, and Earth are positioned at a right angle to each other, the resulting tide is about 20 percent lower than a normal tide.
Low neap tides occur on the seventh/eighth day (सप्तमी/अष्टमी) of the lunar fortnight.
Other Facts
Southampton (England) experiences four tides in a day: two via the English Channel and two via the North Sea.
The Bay of Fundy experiences the highest tides (15 to 18 meters).
Diurnal Tide (दैनिक ज्वार):
A place where a tide occurs only once a day. In this case, the next tide occurs 24 hours and 52 minutes after the previous one.
Objective Questions
1. What are the causes of the generation of tides and ebbs in the oceans?
A. Due to the effect of the Sun
B. Due to the rotational speed of the Earth
C. Due to the combined effect of the Sun and the Moon
D. Due to gravitation, centripetal force, and centrifugal force
Answer: C
2. The highest tides in the world occur in ....
(1) Bay of Bengal
(2) Hudson Bay
(3) Bay of Fundy
(4) Bay of Biscay
Answer: 3