An experimenter finds that no photo-electrons are emitted from tungsten unless the wavelength of light is less than 270nm.
To understand why no photo-electrons are emitted from tungsten unless the wavelength of light is less than 270nm, we need to consider the phenomenon of photoelectric effect.
The photoelectric effect is the emission of electrons from the surface of a material when it is exposed to light or electromagnetic radiation. This effect can be explained using the particle nature of light, as proposed by Albert Einstein.
According to the photoelectric effect, when light falls on a material, it transfers its energy to the electrons present in the material. If the energy of the light is sufficient to overcome the binding energy (also known as work function) of the electrons in the material, the electrons will be emitted.
The energy (E) of a photon of light is related to its wavelength (λ) by the equation: E = hc/λ
Where:
E = Energy of the photon
h = Planck's constant (6.626 x 10^-34 J.s)
c = Speed of light in a vacuum (3.0 x 10^8 m/s)
λ = Wavelength of the light
In the case of tungsten, the absence of photo-electrons unless the wavelength of light is less than 270nm indicates that the binding energy (work function) of electrons in tungsten is such that only photons with energy higher than a certain threshold (corresponding to a wavelength of 270nm or less) can free electrons from the surface.
Therefore, by knowing the wavelength (λ) of the light, we can calculate the energy (E) of the corresponding photon using the equation E = hc/λ. If the energy of the photon is greater than the binding energy of tungsten, photo-electrons will be emitted; otherwise, no electrons will be ejected.
In this case, since the experimenter finds that no photo-electrons are emitted from tungsten unless the wavelength of light is less than 270nm, it implies that the energy of photons corresponding to longer wavelengths (greater than 270nm) is not sufficient to free electrons from tungsten due to its higher work function.