Practice portal › Dual Nature of Matter and Radiation › Conceptual and Statement Questions on the Photoelectric Effect

By applying an electric field of the order of ______ V m⁻¹ to a metal, electrons can be pulled out of the metal.

Asked in GSEB Board March 2020 · Conceptual points of the photoelectric effect

Answer: (3) 10⁸

Step-by-step solution

Idea: this is field emission -- a very strong electric field at a metal surface can drag the free electrons out.

Thermionic emission uses heat and photoelectric emission uses light; field emission uses the electric field alone.

The field required is enormous: of the order of 10⁸ V m⁻¹ (NCERT; a spark plug works this way).

So the answer is 10⁸ V m⁻¹, which is the same as 10⁶ V cm⁻¹.

Why the other options are wrong

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