Question

If a laser light is compose of photons each with an energy of 4.58 × 10−19 J, what is the photon energy of this light in units of nanometers, nm? Report your answer with correct significant figures and correct units.

Answer 1

Answer : The photon energy of this light in units of nanometers, (nm) is,
`4.34* 10^(-2)nm`

Solution :

Formula used :

`E=(h* c)/(\lambda)`

where,

E = energy of photon =
`4.58* 10^(-19)J`

h = Planck's constant =
`6.626* 10^(-34)Js`

c = speed of light =
`3* 10^8m/s`

`\lambda` = wavelength = ?

Now put all the given values in the above formula, we get:

`4.58* 10^(-19)J=((6.626* 10^(-34)Js)* (3* 10^8m/s))/(\lambda)`

`\lambda=4.3017* 10^(-7)m=434.017* 10^(-9)m=434.017nm=4.34* 10^(-2)nm`

conversion used :
`(1nm=1* 10^(-9)m)`

Therefore, the photon energy of this light in units of nanometers, (nm) is,
`4.34* 10^(-2)nm`