explain these two noises from this table

Fundamental Noise Excess Noise Thermal Random motion of electrons in the instrument's |Stray Light any unwanted light that reaches the detector, such (Johnson) electronic components due to temperature as light scattering from the instrument's optical components or external light leaking into the system Photon (Shot) Random fluctuations in the arrival of photons at 1/f Noise (Flicker) This is typically due to instability or drift in the the detector instrument over time. Inherent and cannot be entirely eliminated. Can be minimized or controlled through design and calibration