Answer & explanation
Correct answer: option 3
$\lambda = \frac{hc}{\Delta E} = \frac{12400}{2.5} = 5000A^0$
$\text{Any wavelength below this can do the job so correct option is }4000A^0.$
Correct answer: option 3
$\lambda = \frac{hc}{\Delta E} = \frac{12400}{2.5} = 5000A^0$
$\text{Any wavelength below this can do the job so correct option is }4000A^0.$