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WAEC Physics 2017 Paper

Question : 30

Total: 50

\mathrm{m\,s^{-1}}

Solution:

Concept:

For a stationary wave between two fixed ends, the length

L

contains a whole number of half-wavelengths.

Explanation:

From the diagram, the distance between the fixed ends spans two full wavelengths, so

L = 2\lambda

Given

L = 4.0\,\mathrm{m}

, we have

2\lambda = 4.0\,\mathrm{m}

Thus,

\lambda = \frac{4.0}{2} = 2.0\,\mathrm{m}

The wave speed is

v = 1.0\,\mathrm{m\,s^{-1}}

Using

v = f\lambda

, we get

f = \frac{v}{\lambda} = \frac{1.0}{2.0} = 0.50\,\mathrm{Hz}

Answer:

Wavelength

= 2\,\mathrm{m}

and frequency

= 0.50\,\mathrm{Hz}

Correct option: C.

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