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JAMB Physics 2013 Paper

Question : 42

Total: 43

(h= 6.63 x 10 ^-34Js, c =3.0 x 10 ⁸ms^-1)

Solution:

Concept:

Photon energy depends on wavelength through Planck's constant and the speed of light.

Explanation:

Use the photon energy formula:

E = \frac{hc}{\lambda}

Given:

h = 6.63 \times 10^{-34}\ \mathrm{J\,s}

c = 3.0 \times 10^{8}\ \mathrm{m\,s^{-1}}

and

\lambda = 10^{-10}\ \mathrm{m}

Substitute the values into the formula:

E = \frac{(6.63 \times 10^{-34})(3.0 \times 10^{8})}{10^{-10}}

Multiply the numerator first:

6.63 \times 3.0 = 19.89

Handle the powers of ten:

10^{-34} \times 10^{8} = 10^{-26}

So:

E = \frac{19.89 \times 10^{-26}}{10^{-10}}

Dividing by

10^{-10}

gives:

E = 19.89 \times 10^{-16}\ \mathrm{J}

Write in standard form:

E = 1.989 \times 10^{-15}\ \mathrm{J}

Rounded to one decimal place:

E \approx 2.0 \times 10^{-15}\ \mathrm{J}

Answer:

Option A:

2.0 \times 10^{-15}\ \mathrm{J}

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