Question

The energy of a photon is $3\times {10}^{-12}$ ergs. Its wavelength (in nm) will be:

• A. $662$
• B. $1324$
• C. $66.2$
• D. $6.62$

Answer 1

The correct option is A $662$

Erg is the dimension of energy in CGS (centimeter-gram-second) system of units.

Therefore, $1\text{erg}={10}^{-7}\text{joules}$.

Now, the energy of photon is $3$ x ${10}^{-19}J$.

Using $E=\frac{h\times c}{\lambda }$,

$\text{Wavelength (nm)}=\frac{3\times {10}^{8}m/s\times 6.626\times {10}^{-34}}{3\times {10}^{-19}J}Js$$=662\text{nm}$.