<u>Answer:</u> The energy of photon is 
<u>Explanation:</u>
The relation between energy and wavelength of light is given by Planck's equation, which is:

where,
E = energy of the light = ?
h = Planck's constant = 
c = speed of light = 
= wavelength of photon = 0.122 m
Putting values in above equation, we get:

Hence, the energy of photon is 
I believe the answer is C
Answer:
C = 18.29 g
Explanation:
Given data:
Mass of beryllium needed = ?
Mass of nitrogen = 18.9 g
Solution:
Chemical equation:
3Be + N₂ → Be₃N₂
now we will calculate the number of moles of nitrogen:
Number of moles = mass/molar mass
Number of moles = 18.9 g/ 28 g/mol
Number of moles = 0.675 mol
Now we will compare the moles of nitrogen and Be from balance chemical equation.
N₂ : Be
1 : 3
0.675 : 3/1×0.675 = 2.03 mol
Number of moles of Be needed are 2.03 mol.
Mass of Beryllium:
Mass = number of moles × molar mass
Mass = 2.03 mol × 9.01 g/mol
Mass = 18.29 g