Question

Be sure to answer all parts. What is the energy (in J) of one photon of 639 nm wavelength light? Enter your answer in scientific notation. Cx10J

Answer 1

1)

Given:
lambda = 6.39*10^-7 m

use:
E = h*c/lambda
=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(6.39*10^-7 m)
= 3.111*10^-19 J
Answer: 3.11*10^-19 J

2)

Given:
lambda = 4.75*10^-7 m
1st calculate energy of 1 photon

use:
E = h*c/lambda
=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(4.75*10^-7 m)
= 4.185*10^-19 J

number of photon = total energy/energy of 1 photon
n = 2.0E-17/4.185*10^-19
= 47.79
Answer: 48