Physics
WAEC 1994
The wave function of a metal is 8.0 x \(10^{-19}\)J. Calculate the wavelength of its threshold frequency. (Speed of light in a vacuum = 3 x \(10^8ms^{-1}, Planck's constant = 6.6 \times 10^{-34}\)Js)
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A.
0.8 x \(10^{-7}\)m
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B.
1 x \(10^{-7}\)m
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C.
2.3 x \(10^{-7}\)m
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D.
3.8 x \(10^{-7}\)m
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E.
12.4 x \(10^{-7}\)m
Correct Answer: Option C
Explanation
\(\theta = E - E_f = h_f = \frac{v}{\lambda} \Rightarrow = \lambda = \frac{h_v}{\theta}
\frac{6.6\times 10^{-34} \times 3 \times 10^{8}}{8.6 \times 10^{-19}} = 0.8 \times 10^{-7}\)m
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