Platinum, which is widely used as a catalyst, has a work function (the minimum energy needed to eject an electron from the metal surface) of 9.05 × 10-¹⁹ J. What is the longest wavelength of light which will cause electrons to be emitted? A) 2.196 × 10^-7 m B) 4.553 × 10^-6 m C) 5.654 × 10² m D) 1.370 × 10¹⁵ m E) 10⁶ m

Question

Platinum, which is widely used as a catalyst, has a work function (the minimum energy needed to eject an electron from the metal surface) of 9.05 × 10-¹⁹ J. What is the longest wavelength of light which will cause electrons to be emitted? A) 2.196 × 10^-7 m B) 4.553 × 10^-6 m C) 5.654 × 10² m D) 1.370 × 10¹⁵ m E) > 10⁶ m

Quizplus · Accepted Answer

The energy of a photon of light is given by E=hc/λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength of light. For an electron to be ejected from the platinum surface, the energy of the photon must be greater than or equal to the work function of platinum. Therefore, we can set E=hc/λ equal to the work function and solve for λ. This gives λ = hc/E = (6.626 × 10^-34 J s) (2.998 × 10^8 m/s) / (9.05 × 10^-19 J) = 2.196 × 10^-7 m. This wavelength corresponds to choice A.

Platinum, Which Is Widely Used as a Catalyst, Has a Work