# Plates made of different materials received the same energy from the light source.

Plates made of different materials received the same energy from the light source. The work of electron output from the surface of lithium is 2.4 eV, and from the surface of zinc – 4.2 eV. From the surface of which metal will electrons fly out with a higher speed during the photoelectric effect?

Avl = 2.4 eV = 3.84 * 10 ^ -19 J.

Abc = 4.2 eV = 6.72 * 10 ^ -19 J.

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

m = 9.1 * 10 ^ -31 kg.

C = 3 * 10 ^ 8 m / s.

Vl -?

Vts -?

When falling, the energy of the light wave Ev goes to tearing out electrons from the surface of the metal Av and imparting kinetic energy Ek to them: Ev = Av + ​​Ek.

The energy of the light wave Ev is determined by the formula: Ev = h * C / λ, where h is Planck’s constant, C is the speed of light, λ is the wavelength.

Let us express the kinetic energy of electrons: Ek = Ev – Av.

Ek = m * V ^ 2/2.

V ^ 2 = 2 * Ek / m = 2 * (Ev – Av) / m.

V = √ (2 * (Ev – Av) / m).

It can be seen from the formula that the larger the work function of the metal, the slower the rate of emission of electrons from the metal.

Vl> Vts.

When Ev <Av, electrons will not fly out of the metal surface at all.

Answer: the rate of release of electrons from the surface of lithium is greater than the rate of release from zinc Vl> Vts.

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