Question

$1$ mole of photon, each of frequency $2500\,s^{-1},$ would have approximately a total energy of :

• A. 1 erg
• B. 1 Joule
• C. 1 eV
• D. 1 MeV

Answer 1

Answer: (A)

1 erg

Answer 2

Frequency of one photon $=2500\, s ^{-1}$
$\therefore$ Frequency of 1 mole of photon
$=6.023 \times 10^{23} \times 2500 \,s ^{-1}$
Total energy of $1$ mole of photon, $E=h v$
$=6.626 \times 10^{-34} \,Js \times 6.023 \times 10^{23} \times 2500\, s ^{-1}$
$=9.97 \times 10^{-7} J \approx 10\, erg$
In option (a) there should be $10$ erg instead of $1$ erg.