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WAEC Physics 2014 Paper

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Question : 29

Total: 48

The diagram above illustrates an electromagnetic wave travelling with speed 3.0 x 10⁸ms^-1. Calculate the wave length of the wave

0.05m
0.15m
0.16m
0.40m

Solution:

Concept:

An electromagnetic wave follows the wave equation

v = f\lambda

.

Explanation:

From the diagram, the frequency is

f = 2.0 \times 10^{9}\ \mathrm{Hz}

.

The speed is given as

v = 3.0 \times 10^{8}\ \mathrm{ms^{-1}}

.

Make wavelength the subject of the formula:

\lambda = \frac{v}{f}

Substitute the known values:

\lambda = \frac{3.0 \times 10^{8}}{2.0 \times 10^{9}} = 0.15\ \mathrm{m}

Answer:

B. 0.15 m

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