Photoelectric Effect

The photoelectric effect occurs when materials emit electrons when exposed to light. Certain materials are photo sensitive to visible light, and their work function determines the wavelength of light required to release electrons.
Caesium, sodium, rubidium, and potassium are photo sensitive to visible light due to their low work functions, allowing them to release electrons when exposed to visible light.
Cadmium, on the other hand, has a higher work function, meaning it is not photo sensitive to visible light and requires ultraviolet light for the photoelectric effect to occur.
Thus, cadmium is the material that is not photo sensitive to visible light.

The correct option is (D) : Cadmium

Step 1: Use the photoelectric equation: , where is the maximum kinetic energy of the ejected electrons, is the energy of the incident photons, and is the work function.
Step 2: The maximum kinetic energy can also be expressed as , where is the stopping potential and is the elementary charge.
Step 3: Setting eV and solving for gives eV.
Step 4: Therefore, the energy of the incident radiation is 11.2 eV.