Question

For which of the following metals, photoelectric effect is possible for visible radiation?

Options

• Zinc

• Cadmium 

• Magnesium

• Sodium

Answer 1

Sodium

Explanation:

Alkali metals (like Na) have low work functions (2.3-2.4 eV), so visible photons (1.8-3.1 eV for 700-400 nm) can eject electrons, whereas metals such as Zn, Cd, and Mg require ultraviolet radiation. This is stated in the text and the table of work functions.