JEE Main · 2011 · 10 Apr 2011 · Offline · Atomic Structure

A gas absorbs a photon of 355 nm and emits at two wavelengths. If one of the emissions is at 680 nm , the other is at :

Answer: (B)

Solution

Energy is conserved between the one photon absorbed and the two emitted, and since photon energy goes as

\frac{1}{λ}

\frac{1}{λ _{abs}} = \frac{1}{λ _{1}} + \frac{1}{λ _{2}}

. With absorption at

355 nm

and one emission at

680 nm

\frac{1}{λ _{2}} = \frac{1}{355} - \frac{1}{680} = \frac{680 - 355}{355 \times 680} = \frac{325}{241400}

, so

λ_{2} \approx 743 nm

JEE Main · 2011 · 10 Apr 2011 · Offline · Single correct option