A Level Physics Practice Exam

What is the time taken for a wave with a frequency of 780Hz to move one wavelength?

1. 1/780 s

2. 780 s

3. 1.28 ms

4. 0.00128 s

The correct answer is: 1/780 s

To determine the time taken for a wave with a frequency of 780 Hz to move one wavelength, we start by utilizing the relationship between frequency, wavelength, and period of a wave. The frequency of a wave, which is given in hertz (Hz), tells us how many cycles of the wave pass a given point per second. The period of the wave, on the other hand, is the time it takes for one full cycle to complete. The relationship between frequency (f) and period (T) can be expressed by the formula: \[ T = \frac{1}{f} \] In this case, the frequency is 780 Hz. By substituting this value into the equation, we find: \[ T = \frac{1}{780} \, \text{s} \] Calculating this gives: \[ T \approx 0.00128 \, \text{s} = 1.28 \, \text{ms} \] This means it takes approximately 1.28 milliseconds for one complete cycle (or one wavelength) to occur. Considering the time for one wavelength corresponds to the period of the wave, this supports the correct interpretation that one wavelength takes the same amount of time as its period