Question

Find the frequency of light that corresponds to photons of energy $5.0\times {10}^{-5}$ erg.

• A. $7.5\times {10}^{-21}se{c}^{-1}$
• B. $7.5\times {10}^{-21}sec$
• C. $7.5\times {10}^{21}se{c}^{-1}$
• D. $7.5\times {10}^{21}sec$

Answer 1

The correct option is C $7.5\times {10}^{21}se{c}^{-1}$

Using $E=hv$,

We get,

$v=\frac{E}{h}=\frac{5.0\times {10}^{-5}erg}{6.63\times {10}^{-34}Js}$

$v=\frac{5.0\times {10}^{-5}erg}{6.63\times {10}^{-34}\times {10}^{7}ergsec}$

$[\because 1J={10}^{7}erg]$

$v=7.54\times {10}^{21}se{c}^{-1}$