The time for one oscillation

The idea

The time period T is the time taken for one complete density oscillation at a fixed point; its SI unit is the second (s).

Ten ups and downs

The density at a fixed point goes through 10 complete oscillations in 2 seconds, one just after another, all taking the same time.

What do you think is the time taken by a single oscillation?

• 0.2 s
• 2 s
• 20 s

Share the time

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Time for one

The time taken for one complete density oscillation at a fixed point is the time period. It is written T and measured in seconds.

The time period T is the time taken for one complete density oscillation at a fixed point. Its SI unit is the second (s).

Notes

The time period T is the time for one complete density oscillation at a fixed point. Its SI unit is the second (s).

Check yourself

What is the time period of a wave?

There are 5 density oscillations in 10 seconds at a fixed position (an example). What is the time period, in s?

Answer: 2 s

Time for one oscillation = 10 s ÷ 5 = 2 s.

There are 20 density oscillations in 4 seconds at a fixed position (an example). What is the time period, in s?

Answer: 0.2 s

Time for one oscillation = 4 s ÷ 20 = 0.2 s.

What is the SI unit of the time period?

• The time taken for one complete density oscillation at a fixed point — correct. Yes!
• The number of oscillations in one second. That is the frequency. The time period is the time taken for one oscillation.
• The distance between two crests. That is the wavelength, measured in metres.
• The hertz (Hz). The hertz is the unit of frequency. The SI unit of time period is the second.
• The second (s) — correct. Yes!
• The metre (m). The metre is the unit of wavelength. The SI unit of time period is the second.