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The work function of a photoelectric material is 4.0 eV. (a) What is the threshold wavelength? (b) Find the wavelength of light for which the stopping potential is 2.5 V.

Shane Macguire

12 Years agoGrade upto college level

1 Answer

Jitender Pal

12 Years ago

Sol. ∅ = 4 eV = 4 * 1.6 *10^-19 J a) Threshold wavelength = λ ∅ = hcλ ⇒ λ = hC/∅ = 6.63 * 10^-34 *3 * 10^8/4 * 1.6 *10^-19 = 6.63 * 3/6.4 * 10^-27/10^-9 = 3.1 * 10^7 m = 310 nm. b) Stopping potential is 2.5 V E = ∅ + eV ⇒ hcλ = 4 * 1.6 * 10^-19 + 1.6 * 10^-19 * 2.5 ⇒ λ = 6.63 *10^-34 *3 * 10^8/λ * 1.6 * 10^-19 = 4 + 2.5 ⇒ 6.63 * 3 * 10^-26/1.6 * 10^-19 * 2.5 = 1.9125 * 10^-7 = 190 nm.

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The work function of a photoelectric material is 4.0 eV. (a) What is the threshold wavelength? (b) Find the wavelength of light for which the stopping potential is 2.5 V.

Shane Macguire

1 Answer

Jitender Pal

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