Answer:
Correct answer: (a) Ekmax = 1.3 · 10⁻¹⁹ J, (b) ε = 5 eV, (c) f = 1.21 · 10¹⁵ Hz
Explanation:
Given:
photon energy ε = 8 · 10⁻¹⁹ J
work function for metal Wf = 6.7 · 10⁻¹⁹ J
(a) Ekmax = ?
The Einstein equation for photo effect is:
ε = Wf + Ekmax ⇒ Ekmax = ε - Wf
Ekmax = 8 · 10⁻¹⁹ - 6.7 · 10⁻¹⁹ = 1.3 · 10⁻¹⁹ J
Ekmax = 1.3 · 10⁻¹⁹ J
(b) ε = ? eV
the relationship between 1 eV and 1 J is:
1 eV = 1.6 · 10⁻¹⁹ J
so the energy of one photon in eV equals:
ε = 8 · 10⁻¹⁹ J = 8 · 10⁻¹⁹ / 1.6 · 10⁻¹⁹ eV = 5 eV
ε = 5 eV
(c) f = ?
the energy of a single photon is calculated according to the formula:
ε = h · f
where is:
h = 6.62 · 10⁻³⁴ J s plank constant
and f frequency of each photon (electromagnetic radiation)
f = ε / h = 8 · 10⁻¹⁹ J / 6.62 · 10⁻³⁴ J s = 1.21 · 10¹⁵ s⁻¹ = 1.21 · 10¹⁵ Hz
f = 1.21 · 10¹⁵ Hz
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