Q. If the wavelength of an electromagnetic radiation is 2000Å, what is its energy in ergs?
A) $9.94 \times 10^{- 12}$
B) $9.94 \times 10^{- 19}$
C) $4.97 \times 10^{- 12}$
D) $4.97 \times 10^{- 19}$
Explanation
(a)
$v = \frac{c}{\lambda} = \frac{3 \times 10^{10}}{2000 \times 10^{- 8}} = 1.5 \times 10^{15}s^{- 1}$
$h = 6.6 \times 10^{- 27}erg\ s.$
$E = hv = 6.6 \times 10^{- 27} \times 1.5 \times 10^{15}$
$= 9.94 \times 10^{- 12}erg$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.