Answer:
n = 2.208x10¹⁸ photons
Explanation:
The energy of a photon( an elementary particle) is given by the equation:
E = nxhxf
Where n is the number of photons, h is plank constant (6,62x10⁻³⁴ J.s), and f is the frequency. Knowing that the power level is 0.120mW (1.2x10⁻⁴ W), the energy in J, for a time of 78 min (4680 s)
E = 1.2x10⁻⁴x4680 = 0.5616 J
The frequency of a photon is its velocity ( c= 3x10⁸ m/s) divided by its wavelength, which is 780 nm = 780x10⁻⁹ m
f = 3x10⁸/780x10⁻⁹
f = 3.846x10¹⁴ s⁻¹
Then, the number of photons is:
0.5616 = nx6,62x10⁻³⁴x3.846x10¹⁴
n = 2.208x10¹⁸ photons.
Answer:

Explanation:
We are given a number of particles and asked to convert to moles.
<h3>1. Convert Particles to Moles </h3>
1 mole of any substance contains the same number of particles (atoms, molecules, formula units) : 6.022 *10²³ or Avogadro's Number. For this question, the particles are not specified.
So, we know that 1 mole of this substance contains 6.022 *10²³ particles. Let's set up a ratio.

We are converting 2.98*10²³ particles to moles, so we multiply the ratio by that value.

The units of particles cancel.



<h3>2. Round</h3>
The original measurement of particles (2.98*10²³) has 3 significant figures, so our answer must have the same.
For the number we found, 3 sig figs is the thousandth place.
The 8 in the ten-thousandth place (0.4948522086) tells us to round the 4 up to a 5 in the thousandth place.

2.98*10²³ particles are equal to approximately <u>0.495 moles.</u>
Answer:different elements have different number of electrons and shells/orbits thatswhy it have different atomic mass and size.
Explanation: