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JAMB Physics 2022 Paper

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Question : 3

Total: 40

Consider the wave equation y = 5mm sin [1cm

^{-1}

^{-1}

t]. The wave number is?

0.1 cm $^{-1}$
10cm $^{-1}$
1.0cm $^{-1}$
2cm $^{-1}$

Solution:

Concept:

The wave number is the coefficient of

x

in a standard wave equation of the form

y = A \sin(kx - \omega t)

.

Explanation:

The given wave equation is

y = 5\,\text{mm} \sin\left[1\,\text{cm}^{-1}x - 60\,\text{s}^{-1}t\right]

.

Compare this with

y = A \sin(kx - \omega t)

.

Here,

k = 1\,\text{cm}^{-1}

, because it is the factor multiplied by

x

inside the sine function.

Therefore, the wave number is

1.0\,\text{cm}^{-1}

.

Answer:

C.

1.0\,\text{cm}^{-1}

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