Question

Wavelength of photon having energy $2.5\text{eV}$:
$(\text{Take Planck's constant},h=6.6\times {10}^{-34}\text{Js})$

• A. $6.20\times {10}^{-3}\stackrel{o}{A}$
• B. $6.20\times {10}^3\stackrel{o}{A}$
• C. $4.95\times {10}^3\stackrel{o}{A}$
• D. $4.95\times {10}^{-3}\stackrel{o}{A}$

Answer 1

The correct option is C $4.95\times {10}^3\stackrel{o}{A}$

We know that,
$1eV=1.6\times {10}^{-19}J$
Again, Energy $\left(E\right)=\frac{hc}{\lambda }$
Where, $\lambda =\text{Wavelength}$
$c=\text{Velocity of light}$
$\therefore \lambda =\frac{hc}{E}=\frac{6.6\times {10}^{-34}\times 3\times {10}^8}{2.5\times 1.6\times {10}^{-19}}=4.95\times {10}^3\stackrel{o}{A}$