Question

What is the energy, in electron volts, of light photons at the ends of the visible spectrum, that is, at wavelength of 380 and 770 nm?

Answer 1

Energy of red photons is about 1.8 electron volts (eV) of energy, while energy of each blue photon transmits about 3.1 eV.

Answer 2

The energy, in electron volts, of light photons at wavelength of 380 and 770 nm are as follows:

• Photons are discrete energy packets with no mass but characteristic wavelength and frequency.
• Energy of photon =

$\frac{hc}{ \lambda}$

• where lambda is the wavelength in m
• h is Planck's constant
• c is speed of light
• Substituting values, we get energy of photon in Joules
• $\frac{6.626× {10}^{ - 34 } \times 3 \times {10}^{8} }{380 \times {10}^{ - 9} } j$
• To convert in eV, divide by 1.602 X 10^-19
• On solving, energy of 380nm photon is 3.26eV
• Similarly solving for 770nm, energy of photon is 1.60eV.