What is the frequency of visible light which has a wavelength of 625nm?

The answer is 4.80 x 1014s-1b

Explanation:

625 nm x 10-9m= 6.25 x 10-7 m = c = 2.998 x 108m/s1 nm 6.25 x 10-7m=4.80 x 1014s-1b.)

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-