Photoelectric Effect

Step 1: Understanding the photoelectric effect and photo cells.
A photo cell, also known as a photovoltaic cell, works on the principle of the photoelectric effect. When light strikes a metal surface in the cell, the energy of the photons causes the emission of electrons. These emitted electrons create an electric current, effectively converting light energy into electrical energy. This process is the basis of solar panels, which use the photoelectric effect to generate electricity from sunlight.
Step 2: The working principle of other devices.
- A Coolidge tube is used to generate X-rays, and it doesn't directly convert light energy to electrical energy.
- A thermocouple generates an electrical current due to temperature differences, not light.
- A cloud chamber is used to detect the paths of charged particles, and it does not convert light energy into electrical energy.
Step 3: Conclusion.
Thus, the correct device that converts light energy into electrical energy is a photo cell, corresponding to option (C).

Step 1: Understanding the photoelectric effect.
The photoelectric effect describes how electrons are emitted from a metal surface when light of sufficient frequency strikes it. The maximum kinetic energy of the emitted photoelectrons is given by the equation: where is Planck's constant, is the frequency of the incident light, and is the work function of the material.
Step 2: Dependence on frequency.
The equation shows that the maximum kinetic energy of the photoelectrons depends directly on the frequency of the incident light. The higher the frequency, the greater the energy of the emitted photoelectrons.
Step 3: Conclusion.
Thus, the maximum kinetic energy of the photoelectrons depends only on the frequency of the incident light, corresponding to option (B).

Threshold wavelength is the minimum wavelength of light that can cause the emission of electrons from a metal surface. It is related to the threshold frequency by the equation: where is the threshold wavelength, is the speed of light, and is the threshold frequency.
Threshold frequency is the minimum frequency of light required to release electrons from the metal surface in the photoelectric effect. It is given by the equation: where is the threshold energy (the energy required to free an electron) and is Planck's constant.