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JAMB Physics 2023 Paper

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Question : 24

Total: 65

Light of wavelength 589 nm in vacuum passes through a piece of fused quartz of index of refraction n = 1.458. What is the frequency of the light in fused quartz?

[Speed of light c =

3.00 \times 10^8 \mathrm{m\,s}^{-1}

]

$5.09 \times 10^{15}$ Hz
$5.09 \times 10^{14}$ Hz
$1.77 \times 10^{15}$ Hz
$1.77 \times 10^{14}$ Hz

Solution:

n=1.458, c= $3.00 \times 10^8 \mathrm{m\,s}^{-1}$ ,λo = 589nm; f=?

Speed of light in a medium (v)=

\frac{c}{n}

where n is the refractive index of the medium

⇒λn=

\frac{589}{1.458}

= 404nm

v=fλ

⇒f=

\frac{v}{\lambda}

=

\frac{2.06 \times 10^8}{404 \times 10^{-9}}

1\text{ nano}=10^{-9}

∴f=

5.09 \times 10^{14}

Hz

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