Question

Робота виходу електронів для вольфраму становить 4,5 ев (1 ев = 1,6 D10 9.Дж). За якого граничного значення довжини хвилі випромінювання можливий фотоефект? Сталу Планка вважайте рівною 6,6 D 10-34 Дж Пс, швидкість світла 3 D 108 м/с.​

Answer 1

The Relationship Between Work Function and Wavelength in the Photoelectric Effect

The photoelectric effect refers to the phenomenon where electrons are emitted from a material when it is exposed to light. The energy required to remove an electron from a material is known as the work function. In this case, we are considering the work function of tungsten, which is given as 4.5 eV.

To determine the maximum wavelength of radiation that can cause the photoelectric effect, we can use the equation:

E = hf

where: - E is the energy of a photon, - h is Planck's constant (6.6 x 10^-34 J·s), - f is the frequency of the radiation.

We can relate the frequency of the radiation to its wavelength using the equation:

c = λf

where: - c is the speed of light (3 x 10^8 m/s), - λ is the wavelength of the radiation.

By substituting the expression for frequency (f = c/λ) into the equation E = hf, we can rewrite it as:

E = hc/λ

Now, we can solve for the maximum wavelength (λ) that can cause the photoelectric effect by rearranging the equation:

λ = hc/E

Substituting the values given in the question, we have:

λ = (6.6 x 10^-34 J·s) x (3 x 10^8 m/s) / (4.5 eV x 1.6 x 10^-19 J/eV)

Simplifying the equation, we find:

λ ≈ 2.75 x 10^-7 m

Therefore, the maximum wavelength of radiation that can cause the photoelectric effect for tungsten, given a work function of 4.5 eV, is approximately 2.75 x 10^-7 meters.

Please note that the above calculation assumes that the energy of a photon is equal to the work function of the material. In reality, the photoelectric effect can occur for photons with energies greater than the work function, resulting in electrons being emitted with kinetic energy.