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WAEC Physics 2012 Paper

Question : 44

Total: 47

Solution:

Concept:

Photoelectric effect: the ejected electron’s kinetic energy is the photon energy minus the work function of the metal.

Explanation:

The photoelectric equation is:

K_{\text{max}} = hf - W_0

Here, photon energy

hf = 4.0\ \mathrm{eV}

and work function

W_0 = 3.0\ \mathrm{eV}

Substitute the values:

K_{\text{max}} = 4.0\ \mathrm{eV} - 3.0\ \mathrm{eV} = 1.0\ \mathrm{eV}

Since the result is positive, an electron is ejected with this kinetic energy.

Answer:

1.0\ \mathrm{eV}

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