Answer:
f = 1.18 x 10¹¹ Hz
Explanation:
The equation used to find frequency is:
f = c / w
In this form, "f" represents the frequency (Hz), "c" represents the speed of light (3.0 x 10⁸ m/s), and "w" represents the wavelength (m).
Since you have been given the value of the constant (c) and wavelength, you can substitute these values into the equation to find frequency.
f = c / w <---- Formula
f = (3.0 x 10⁸ m/s) / w <---- Plug 3.0 x 10⁸ in "c"
f = (3.0 x 10⁸ m/s) / (2.55 x 10⁻³ m) <---- Plug 2.55 x 10⁻³ in "w"
f = 1.18 x 10¹¹ Hz <---- Divide
Answer:
Explanation:
The energy of a photon is given by the equation 
, where h is the <em>Planck constant</em> and f the frequency of the photon. Thus, N photons of frequency f will give an energy of 
.
We also know that frequency and wavelength are related by 
, so we have 
, where c is the <em>speed of light</em>.
We will want the number of photons, so we can write
We need to know then how much energy do we have to calculate N. The equation of power is 
, so for the power we have and considering 1 second we can calculate the total energy, and then only consider the 4% of it which will produce light, or better said, the N photons, which means it will be 
.
Putting this paragraph in equations:
.
And then we can substitute everything in our equation for number of photons, in S.I. and getting the values of constants from tables:
