why Photo electric effect does not work below minimum threshold frequency
The photoelectric effect is a phenomenon in which electrons are emitted from a material when it is exposed to light (photons). However, there is a minimum threshold frequency or energy associated with the incident light below which the photoelectric effect will not occur, regardless of the light's intensity.
The threshold frequency or energy is determined by the work function of the material, which is the minimum energy required to remove an electron from the material's surface. This work function is characteristic of the material and depends on its atomic structure.
why the photoelectric effect may not work if the incident light has low frequency.
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Energy of Photons: In the photoelectric effect, it's the energy of individual photons that matters. The energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength, as given by the equation: E = h * f, where E is energy, h is Planck's constant, and f is frequency.
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Threshold Frequency: To eject an electron from a material, the energy of the incident photons must be greater than or equal to the work function of the material. If the incident photons have a frequency (or energy) below this threshold, they won't have enough energy to overcome the work function, and the photoelectric effect won't occur.
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Visible Light and Threshold Frequency: Light in the visible spectrum has different colors corresponding to different wavelengths. Red light has longer wavelengths (around 620-750 nm), while violet light has shorter wavelengths (around 380-495 nm). The threshold frequency (and energy) required for the photoelectric effect depends on the material.
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Threshold Frequency vs. Wavelength: Wavelength and frequency are inversely related. Longer wavelengths correspond to lower frequencies. Therefore, if the incident light has a wavelength in the red part of the spectrum, it means that its frequency is lower than what is typically needed to overcome the work function of most materials. As a result, the photoelectric effect won't be observed with such light.