High Tide, Low Tide

1. What are the causes of high-tide low tide formation in the oceans? [U.P.P.C.S. (Pre) 1991]

(a) Due to the effect of the sun
(b) Due to the rotation of the Earth
(c) Due to the combined effect of sun and the moon
(d) Due to Gravitation, Centripetal force and the centrifugal force

Correct Answer: (d) Due to Gravitation, Centripetal force and the centrifugal force

Solution:High tide/low tide occurs as a result of the force of gravitational pull between the Earth and the Moon and the two forces viz centripetal force and centrifugal force produced upon the Earth. Ocean water is kept at equal levels around the planet by the Earth's gravity pulling inward, but Moon's gravitational force is strong enough to disrupt this balance by accelerating the water in that hemisphere which faces the Moon. When the Moon's force of attraction is stronger than the centrifugal force of the Earth, high tides occur. On the other hand, when the centrifugal force is stronger than the Moon's force of attraction tides (Indirect high tide) occur. Between these two high tides water level becomes down that is called low Tides (ebb). Earth experiences high and low tides twice in 24 hours and 50 minutes.

2. Tides occur in oceans and seas due to which among the following? [I.A.S. (Pre) 2015]

1. Gravitational force of Sun

2. Gravitational force of Moon

3. Centrifugal force of Earth

Select the correct answer using the codes given below:

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Correct Answer: (d) 1, 2 and 3

Solution:High tide/low tide occurs as a result of the force of gravitational pull between the Earth and the Moon and the two forces viz centripetal force and centrifugal force produced upon the Earth. Ocean water is kept at equal levels around the planet by the Earth's gravity pulling inward, but Moon's gravitational force is strong enough to disrupt this balance by accelerating the water in that hemisphere which faces the Moon. When the Moon's force of attraction is stronger than the centrifugal force of the Earth, high tides occur. On the other hand, when the centrifugal force is stronger than the Moon's force of attraction tides (Indirect high tide) occur. Between these two high tides water level becomes down that is called low Tides (ebb). Earth experiences high and low tides twice in 24 hours and 50 minutes.

3. The cause of producing indirect high tide is – [R.A.S./R.T.S. (Pre) 1999]

(a) Gravitational force of the Moon
(b) Gravitational force of the Sun
(c) Centrifugal force of the Earth
(d) Gravitational force of the Earth

Correct Answer: (c) Centrifugal force of the Earth

Solution:High tide/low tide occurs as a result of the force of gravitational pull between the Earth and the Moon and the two forces viz centripetal force and centrifugal force produced upon the Earth. Ocean water is kept at equal levels around the planet by the Earth's gravity pulling inward, but Moon's gravitational force is strong enough to disrupt this balance by accelerating the water in that hemisphere which faces the Moon. When the Moon's force of attraction is stronger than the centrifugal force of the Earth, high tides occur. On the other hand, when the centrifugal force is stronger than the Moon's force of attraction tides (Indirect high tide) occur. Between these two high tides water level becomes down that is called low Tides (ebb). Earth experiences high and low tides twice in 24 hours and 50 minutes.

4. Statement (A) : During the times of neap-tide, high-tide is below normal and low-tide is above normal. [I.A.S. (Pre) 1998]

Reason (R) : Neap-tides occurs during the new-moon instead of full-Moon.

Choose the correct answer using following options –

(a) (A) and (R) both are correct, and (R) is correct explanation of (A).
(b) (A) and (R) both are correct, and (R) is not correct explanation of (A).
(c) (A) is correct, but (R) is wrong.
(d) (A) is wrong, but (R) is correct.

Correct Answer: (c) (A) is correct, but (R) is wrong.

Solution:During the neap-tides, high-tide remains to be 20% less than the normal and low-tide at this time remains to be higher than the normal. Neap-tide opposite to the spring-tide doesn't occur at New-moon or full-moon but on 7th or 8th days from these two extremes. Therefore, statement (A) is correct but the reason (R) is wrong.

5. In which one of the following positions given in the figure sea-tide would have maximum height? [I.A.S. (Pre) 1999]

(a) M₁
(b) M₂
(c) M₃
(d) M₄

Correct Answer: (d) M₄

Solution:In the figure, M₂ is the position of Full Moon and M₄ is the position of New Moon. In both of these positions, the Sun, the Moon, and the Earth remain in linear position and this situation is known as "Syzygy." In both of these situations, spring tides occur. Perigean spring tide occurs at New Moon or Full Moon and closest to Earth. During New Moon's (closest) Perigean spring tides occur.

6. Spring Tide occurs: [U.P.P.C.S. (Pre) 1999]

(a) When the Sun, the Earth, and Moon are in a straight line
(b) When the Sun and Moon make a right angle
(c) When a strong wind blows
(d) When the night is very cold

Correct Answer: (a) When the Sun, the Earth, and Moon are in a straight line

Solution:In the figure, M₂ is the position of Full Moon and M₄ is the position of New Moon. In both of these positions, the Sun, the Moon, and the Earth remain in linear position and this situation is known as "Syzygy." In both of these situations, spring tides occur. Perigean spring tide occurs at New Moon or Full Moon and closest to Earth. During New Moon's (closest) Perigean spring tides occur.

7. The high tide in the Ocean is caused by [47ᵗʰ B.P.S.C. (Pre) 2005]

(a) Earthquake
(b) Sun
(c) Stars
(d) Moon

Correct Answer: (d) Moon

Solution:Spring-tide occurs in the ocean on the day of Full Moon or New Moon, while at 7ᵗʰ or 8ᵗʰ day after the Full Moon and the New Moon neap-tide occurs. Since the Moon is more near to the Earth in comparison to other stars, so its gravitational force has a greater effect upon the Earth. Due to this effect, high sea waves are produced in oceans. Tide producing power of the Moon is 2.17 times more than the Sun.