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WAEC Physics 2020 Paper

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Question : 38

Total: 51

Water waves have a wavelength of 3.6 cm and speed of

18\ \mathrm{cm\,s}^{-1}

in deep water. If the waves enter shallow water with wavelength of 2.0 cm , calculate the speed of the waves in the shallow water.

$0.4\ \mathrm{cm\,s}^{-1}$
$2.5\ \mathrm{cm\,s}^{-1}$
$10.0\ \mathrm{cm\,s}^{-1}$
$10.8\ \mathrm{cm\,s}^{-1}$

Solution:

Velocity

=

frequency x wavelength

v=18\ \mathrm{cm}/\mathrm{s}

, wavelength

=3.6\ \mathrm{cm}

, then

F=5

hertz

therefore, the speed of the wave in the shallow water

=5 \times 2=10\ \mathrm{cm}/\mathrm{s}

NOTE; as a general rule, the frequency of a wave remains constant while speed and wavelength change as it travels from one medium to another.

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