UPSC Prelims 2001 Q32: Geography – Oceanography
Assertion (A): During the Neap Tides, the high tide is lower and the low tide is higher than
usual. Reason (R): The Neap Tide, unlike the Spring Tide, occurs on the New Moon instead of on
the Full Moon.
- (a) Both A and R are individually true, and R is the correct explanation of A
- (b) Both A and R are individually true, but R is NOT a correct explanation of A
- (c) A is true, but R is false
- (d) A is false, but R is true
Answer: (c) A is true, but R is false
Explanation
Assertion-Reason: neap tides and spring tides
| Statement | Verdict |
|---|---|
| A. In neap tides the high tide is lower and the low tide higher than usual | True — the tidal range is smallest |
| R. Neap tides occur on the new moon instead of the full moon | False — neap tides occur at the first and last quarter (half moon) |
| Spring tide | New moon and full moon — Sun, Moon and Earth in a line; largest range |
| Neap tide | Sun and Moon at right angles to the Earth; pulls partly cancel |
At neap tide the Sun and Moon pull at right angles, so tides are weak: high tides are lower and low tides are higher than usual. Neap tides come about seven days after spring tides, at the quarter moons. Both new moon and full moon give spring tides, so R is false.
Answer: (c) A is true, but R is false.
Why each option is right or wrong
- (a) Incorrect. R is false; neap tides come at the quarter moons.
- (b) Incorrect. R is false, so both cannot be true.
- (c) CORRECT. A describes neap tides correctly; R gives the wrong moon phase.
- (d) Incorrect. A is true; the tidal range is smallest at neap tide.
Key point
Spring tide = syzygy (new and full moon); neap tide = quadrature (quarter moons); about two of each a month.
Remember
Neap tide: quarter moons, smallest range.
Common mistakes
- Thinking new moon gives neap tides because the Moon is 'not seen'.
- Mixing up which tide has the larger range.
- Forgetting that spring tides have nothing to do with the spring season.
Exam tip
Straight line (new or full moon) = spring; right angle (quarter moon) = neap.
Sources
- NCERT Class XI — Fundamentals of Physical Geography, chapter 'Movements of Ocean Water' (tides)
- NOAA National Ocean Service — Tides and Water Levels: spring and neap tides