Alaser produces 17.0 mw of light. in 4.00 hr , the laser emits 6.04×1020 photons. what is the wavelength of the laser?

λ = 490.81 nm

Explanation:

The first thing we need to do is use the correct units. Let's convert the mW to J/s.

1 Watt > 1 J/s

And we have 17 mW:

1 Watt > 1000 mW

Therefore, converting the mili watts to J/s we have:

17 mW * 1 J/s / 1000 mW = 0.017 J/s

Now, we have 4 hours, and in 1 hour we have 3600 seconds so:

t = 4 * 3600 = 14,400 s

Now, the expression to calculate the wavelength is the following:

E = hc/λ (1)

Where:

E: Energy emmited by the laser by photons (J)

h: Planck constant = 6.626x10⁻³⁴ J.s

c: speed of light = 3x10⁸ m/s

λ: wavelength (nm)

Now, we have the Power of the laser, but not the energy emmited by photons. Let's calculate that value:

E = 0.017 J/s * 14,400 s / 6.04x10²⁰

E = 4.05x10⁻¹⁹ J

Now that we have the value of Energy, we just solve for Lambda from (1) to get the wavelength:

λ = hc/E (2)

Now, all we have to do is replace the obtained values and solve for the wavelength:

λ = (6.626x10⁻³⁴ J.s * 3x10⁸ m/s) / 4.05x10⁻¹⁹ J

λ = 490.81x10⁻⁹ m

And to get this value to nanometers (The usual unit of wavelength):

1 m > 1x10⁹ nm

Therefore:

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.