A laser produces red light of wavelength 632.8 nm. Calculate the energy,

Answer:

189.2 KJ

Explanation:

Provided Data

light wavelength = 632.8 nm

Convert nm to meters

1 nm = 1 x 10⁻⁹

632.8 nm = 632.8 x 1 x 10⁻⁹ = 6.328 x 10⁻⁷m

What is the energy of 1 mole of photons?

Solution

Used Formula

                     E = hc/λ

where

E = energy per photon

h = Planck's Constant

Planck's Constant = 6.626 x 10⁻³⁴ Js

c = speed of light

speed of light = 3 × 10⁸ ms⁻¹

λ = wavelength of light

Insert values into the equation

                   E = hc/λ

                   E = 6.626 x 10⁻³⁴ Js ( 3 × 10⁸ ms⁻¹ / 6.328 x 10⁻⁷m)

                   E = 6.626 x 10⁻³⁴ Js (4.741 x 10¹⁴s⁻¹)

                  E = 3.141 x 10⁻¹⁹J

3.141 x 10⁻¹⁹J indicates the energy for a single photon

Next, we need to determine the energy for 1 mole of photons

It is known that

1 mole contains 6.022 x10²³ photons

Consequently,

     Energy for one mole of photons = 3.141 x 10⁻¹⁹J x  6.022 x10²³

     Energy for one mole of photons = 1.89 x 10⁵ J

Now convert J to KJ

1000 J = 1 KJ

1.89 x 10⁵ J = 1.89 x 10⁵ /1000 = 189.2 KJ

Thus,

the energy for one mole of photons is 189.2 KJ