Question

The line spectrum of lithium has a red line at 670.8 nm. Calculate the energy of a photon with this wavelength.

Answer 1

Answer: The energy of the photon having the given wavelength is $2.96\times 10^{-19}J$

Explanation:

We are given:

Wavelength of microwave = $670.8nm=670.8\times 10^{-9}m$    (Conversion factor:  $1m=10^9nm$  )

To calculate the energy of one photon, we use Planck's equation, which is:

$E=\frac{hc}{\lambda}$

where,

h = Planck's constant = $6.625\times 10^{-34}J.s$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength = $670.8\times 10^{-9}m$

Putting values in above equation, we get:

$E=\frac{6.625\times 10^{-34}J.s\times 3\times 10^8m/s}{670.8\times 10^{-9}m}\\\\E=2.96\times 10^{-19}J$

Hence, the energy of the photon having the given wavelength is $2.96\times 10^{-19}J$

Answer 2

3x10^8 / (670.8 * 10^-9) =4.47x10^14 Hz 4.47x10^14 Hz multiplied by plank's constant = 2.9634x10^-19

2.96 x10-19 J