Answer:
B
Explanation:
its upside down but I'm 99% sure
A. Cs - 55 electrons, 55 protons, 77 neutrons
B. Co - 27 electrons, 22 protons, 32 neutrons
C. Tm - 69 electrons, 69 protons, 94 neutrons
D. Zn - 30 electrons, 30 protons, 40 neutrons
For any neutral atom, protons = electrons = atomic number. Neutrons = atomic mass - atomic number.
The best option is melting point
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.
