Photoelectric effect: When a certain metal is illuminated by light, photoelectrons are observed provided that the wavelength of the light is less than 669 nm. Which one of the following values is closest to the work function of this metal? (h = 6.626 × 10^-34J ∙ s, c = 3.00 × 10⁸ m/s, 1 eV = 1.60 × 10^-19 J) A) 1.9 eV B) 2.0 eV C) 2.2 eV D) 2.3 eV

Question

Quizplus · Accepted Answer

The work function is given by the equation:$$W = hc/\lambda$$where:* W is the work function in joules* h is Planck's constant (6.626 × 10^-34 J s)* c is the speed of light (3.00 × 10^8 m/s)* λ is the wavelength in metersSubstituting the given values into the equation, we get:$$W = (6.626 × 10^-34 J s)(3.00 × 10^8 m/s)/(669 × 10^-9 m) = 2.99 × 10^-19 J$$Converting to electron volts, we get:$$W = (2.99 × 10^-19 J)/(1.60 × 10^-19 J/eV) = 1.87 eV$$The closest value to this is 1.9 eV, which is choice A.

Photoelectric Effect: When a Certain Metal Is Illuminated by Light