Conductivity Thermal And Electrical

Conductivity of a substance is determined by the number of free ions or mobile electrons it has. Conductivity increases with the ability of the material to allow charge flow.

1. Step 1: Analyze the conductivity of each metal. - Ag (Silver): Silver has the highest conductivity because it has the highest number of free electrons, and it is an excellent conductor. - Cu (Copper): Copper also has a high conductivity, although it is slightly less than silver. - Na (Sodium): Sodium is an alkali metal, and although it is a good conductor in its ionic form in solution, its metallic conductivity is lower compared to copper and silver. - Fe (Iron): Iron has the lowest conductivity among the listed elements because it has fewer free electrons compared to the others. Thus, the order of conductivity is Ag > Cu > Na > Fe.

Step 1: Understanding the problem.
In the photoelectric effect, the energy of incident photons is used to overcome the work function and the remaining energy is transferred as kinetic energy to the emitted electrons. The kinetic energy of an electron is given by: where is the energy of the incident photon and is the work function of the metal.
Step 2: Calculating velocities.
For , the energy of the photons is , and for this case, the velocity of the emitted electron is . So, the kinetic energy will be: Thus, . For , the energy of the photons is , and the velocity of the emitted electron is . Thus, the kinetic energy is: Hence, .
Step 3: Velocity ratio.
The ratio of the velocities is: This shows that , which matches the option .
Final Answer: .