Question

If the threshold energy for ejection of electron from metal is 1.4 eV and light of 3eV falls on the metal, then the kinetic energy of photoelectron emitted will be:

• A. $2.6\times {10}^{-19}J$
• B. $1.6\times {10}^{-18}J$
• C. $2.2\times {10}^{-19}J$
• D. $3.2\times {10}^{-20}J$

Answer 1

Answer: (A)

$2.6\times {10}^{-19}J$

Threshold energy $=1.4eV$

Energy of light $=3eV$

Kinetic energy $=(3-1.4)eV$

$=1.6eV=1.6\times 1.6\times {10}^{-19}$ joule

$=2.56\times {10}^{-19}$ joule

$=2.6\times {10}^{-19}$ joule.