Question

In order to break a chemical bond in the molecules of human skin, causing sunburn, a photon energy of about $3.5eV$ is required. This corresponds to wavelength in the

• A. Infrared region
• B. X-ray region
• C. Visible region
• D. Ultraviolet region

Answer 1

The correct option is D Ultraviolet region

Converting the energy into joules and using the equation.
$E=\frac{hc}{\lambda }$

$E=3.5eV=3.5\times 1.6\times {10}^{-19}=5.6\times {10}^{-19}J$

$\lambda =\frac{hc}{E}=\frac{6.64\times {10}^{-34}\times 3\times {10}^8}{5.6\times {10}^{-19}}=355nm$

$355nm$ falls in the UV region.