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WAEC Physics 2023 Paper

Question : 3

Total: 50

Solution:

Concept:

The frequency of a wave on a vibrating wire is given by

v = f\lambda

Explanation:

The length of the wire is

125\,\text{cm} = 1.25\,\text{m}

The diagram shows the wire vibrating in five loops, meaning five half-wavelengths fit along the wire.

So,

5 \times \frac{\lambda}{2} = 1.25

This gives

\lambda = \frac{2 \times 1.25}{5} = 0.50\,\text{m}

The speed of the wave is

v = 120\,\text{m/s}

Using

v = f\lambda

, we get

120 = f \times 0.50

Therefore,

f = \frac{120}{0.50} = 240\,\text{Hz}

Answer:

The frequency of the waves is

240\,\text{Hz}

Correct option: A.

240\,\text{Hz}

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