Question

Which of the following Period(s) correspond(s) to wind waves?

• A. 5 seconds
• B. 20 seconds
• C. 6 hours
• D. 12 hours

Hint:

Wind waves have periods of a few seconds up to a few tens of seconds. Tides are much longer (hours). Always check the order of magnitude: seconds = waves, hours = tides.

Answer 1

The Correct Option is A, B

Step 1: Classification of ocean surface waves by period.
- Capillary waves: \(< 1~\text{s}\).
- Wind waves (sea): Typically \(1 - 30~\text{s}\). Generated directly by local winds.
- Swell waves: Long-period waves, often \(10 - 30~\text{s}\), that have propagated away from the wind source.
- Tides: Periods of hours (≈ 6 h, 12 h, etc.).


Step 2: Compare given options.
- (A) \(5~\text{s}\): falls within wind-wave range.
- (B) \(20~\text{s}\): also within long wind waves/swell range.
- (C) \(6~\text{h}\): belongs to semidiurnal tide cycle, not wind waves.
- (D) \(12~\text{h}\): belongs to principal lunar tide cycle, not wind waves.


Step 3: Conclude.
Wind waves correspond to periods of \(\sim 1-30~\text{s}\), so both 5 s and 20 s are correct. Final Answer:
\[ \boxed{5~\text{seconds and } 20~\text{seconds}} \]