# If the maximum wavelength of radiation capable of causing the photoelectric effect in platinum

If the maximum wavelength of radiation capable of causing the photoelectric effect in platinum is 0.234 microns, then when platinum is irradiated with radiation with a frequency of 1.5 ∙ 10 -15 Hz, the maximum kinetic energy of the ejected electrons will be equal to.

λcr = 0.234 μm = 0.234 * 10 ^ -6 m.

v = 1.5 * 10 ^ 15 Hz.

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

c = 3 * 10 ^ 8 m / s.

m = 9.1 * 10 ^ -31 kg.

V -?

The longest wavelength that causes the phenomenon of the photoelectric effect is called the red border of the photoeffect λcr.

The work function of electrons from platinum Av is found by the formula: Av = h * s / λcr, where h is Planck’s constant, c is the speed of light.

Av = 6.6 * 10 ^ -34 J * s * 3 * 10 ^ 8 m / s / 0.234 * 10 ^ -6 m = 84.6 * 10 ^ -20J.

Let’s write down the law of the photoelectric effect: h * v = Av + m * V ^ 2/2.

m * V ^ 2/2 = h * v – Av.

V = √ (2 * h * v / m – 2 * Av / m).

V = √ (2 * 6.6 * 10 ^ -34 J * s * 1.5 * 10 ^ 15 Hz / 9.1 * 10 ^ -31 kg – 2 * 84.6 * 10 ^ -20 J / 9 , 1 * 10 ^ -31 kg) = 0.565 * 10 ^ 6 m / s.

Answer: electrons have a speed V = 0.565 * 10 ^ 6 m / s.

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