Question

ehat is the no. of photons of light with wavelength 4000pm that provide 1j of energy

Answer 1

Hello!

• λ = 4000 pm = 4000 × 10⁻¹² m
• c = Velocity of light in vacuum = $\bf{3 \:x\: 10^{8} \:ms^{-1}}$
• h = Planck’s constant = $\bf{6.626 \:x\:10^{-34}\:Js}$

Then,

Energy = $\dfrac{\sf hc}{\sf \lambda}$ = $\sf 4.965\: x\: 10^{-16} \:J$

$\bf{Now}$ :
1 J will be the Energy = $\dfrac{\sf 1}{\sf 4.965 \:x \:10^{-16} \:J}$ = $\boxed{\sf 2.014 \:x\: 10^{15} \:photons}$

Cheers!