Question

There are found X-Rays with energy ranging from 2 KeV to 5 KeV. What is the minimum and maximum wavelength of X- Ray photon present respectively? (Take hc to be 1242 eV-nm)

• A. 0.248 nm and 0.540 nm
• B. 0.340 nm and 0.621 nm
• C. 0.248 nm and 0.621 nm
• D. 0.340 nm and 0.540 nm

Answer 1

The correct option is C

0.248 nm and 0.621 nm

For the energy of photon we have equation; $E=\frac{hc}{\lambda }$
Looking at the equation we can say that, when the energy is maximum, the wavelength is minimum and when the energy is minimum, the wavelength is maximum.
Now, minimum energy we have is 2KeV.
Hence ${\lambda }_{max}=\frac{hc}{E_{min}}$
$\Rightarrow {\lambda }_{max}=\frac{1242eV-nm}{2000eV}=0.621nm$
Similarly, ${\lambda }_{min}=\frac{hc}{E_{max}}$
$\Rightarrow {\lambda }_{min}=\frac{1242eV-nm}{50000eV}=0.248nm$