Question

A laser emits light with a wavelength of 555nm, containing 4.58 mJ of energy. How many photons are present in the laser?

a) 2.45 x 10^18 photons
b) 3.27 x 10^18 photons
c) 4.58 x 10^18 photons
d) 6.89 x 10^18 photons

Answer 1

To determine the number of photons in the laser, use the equation E = nhf and rearrange it to solve for n. Given the energy and wavelength of the laser, plug in the values to calculate the number of photons. The laser contains approximately 2.45 x 10¹⁸ photons.

So, the correct answer is A.

Step-by-step explanation:

In order to determine the number of photons in the laser, we can use the equation:

E = nhf

where E is the energy of the laser, n is the number of photons, h is Planck's constant (6.63 x 10^-34 J s), and f is the frequency of the light. We can rearrange the equation to solve for n:

n = E / (hf)

Given that the wavelength of the light is 555 nm (or 555 x 10⁻⁹ m), we can convert it to frequency using the equation:

c = λf

where c is the speed of light (3 x 10⁸ m/s) and λ is the wavelength.

f = c / λ

Substituting this into the equation for n, we get:

n = E / [(hc) / λ]

Calculating the values with the given information, we find that there are approximately 2.45 x 10¹⁸ photons present in the laser.

So, the correct answer is A.