For a particular metal, the red line of the photoelectric effect is light at 690 nm. Determine the work function

| June 20, 2021 | education

For a particular metal, the red line of the photoelectric effect is light at 690 nm. Determine the work function of an electron from this metal and the maximum speed that electrons will acquire under the action of radiation with a wavelength of 190 nm.

λcr = 690 nm = 690 * 10 ^ -9 m.

m = 9.1 * 10 ^ -31 kg.

λ = 190 nm = 190 * 10 ^ -9 m.

s = 3 * 10 ^ 8 m / s.

h = 6.6 * 10 ^ -34 J * s.

Av -?

V -?

The work function Av of the material is determined by the formula: Av = h * s / λcr, where h is Planck’s constant, c is the speed of light, λcr is the wavelength at which the photoeffect will be observed.

Av = 6.6 * 10 ^ -34 J * s * 3 * 10 ^ 8 m / s / 690 * 10 ^ -9 m = 0.0286 * 10 ^ -17 J.

Let us write down the formula for the photoelectric effect: h * c / λ = Av + ​​m * V ^ 2/2, where m is the mass of an electron, V is the speed of electron emission from the metal surface.

V = √ (2 * h * s / λ * m – 2 * Av / m).

V = √ (2 * 6.6 * 10 ^ -34 J * s * 3 * 1 ^ 08 m / s / 190 * 10 ^ -9 m * 9.1 * 10 ^ -31 kg – 2 * 0.0286 * 10 ^ -17 J / 9.1 * 10 ^ -31 kg) = 0.129 * 10 ^ 7 m / s.

Answer: Av = 0.0286 * 10 ^ -17 J, V = 0.129 * 10 ^ 7 m / s.



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