Question

The energy in eV for light with a wavelength of 6250 angstroms is _. Note - there are 1.6 x 10-12 erg in 1 eV.

Answer 1

2 eV

Step-by-step explanation:

The energy of a photon of light is given by the formula

`E=(hc)/(\lambda)`

where

h is the Planck constant

c is the speed of light

`\lambda` is the wavelength of the photon

In this problem we have:

`h=6.63\cdot 10^(-34) Js`

`c=3.0\cdot 10^8 m/s`

`\lambda=6250 A = 6250\cdot 10^(-10) m` is the wavelength of the photon

Therefore, the energy in Joules is

`E=((6.63\cdot 10^(-34))(3.0\cdot 10^8))/(6250\cdot 10^(-10))=3.2\cdot 10^(-19)J`

We want to convert this energy into electronvolts: we know that the conversion factor is

`1 eV = 1.6\cdot 10^(-19)J`

Therefore,

`E=(3.2\cdot 10^(-19))/(1.6\cdot 10^(-19))=2 eV`