molarity of a solution means mols per liter.
First, you need to convert 23 grams on NaCl into mols. 23g divided by molar mass (58.44g/mol) which gives you .394 mols.
Now, you need to convert 500ml to L which moves the decimal three places to the left, giving you .500L of solution.
Finally, divide the mols over solution to get .787M
<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 