The kilogram is the SI unit of mass and it is the almost universally used standard mass unit. The associated SI unit of force and weight is the Newton, with 1 kilogram weighing 9.8 Newtons under standard conditions on the Earth's surface.
Explanation:
It is given that,
The thinnest soap film appears black when illuminated with light with a wavelength of 535 nm, 
Refractive index, 
We need to find the thickness of soap film. The soap film appear black means there is an destructive interference. The condition for destructive interference is given by :
t = thickness of film
m = 0,1,2....
= refractive index
For thinnest thickness, m = 1
Hence, this is the required solution.
In the periodic table, calcium is located at the 2nd column of the 4th row starting from the hydrogen gas.
Calcium is very essential in the human body is it helps maintain a healthy teeth and all other bones. Other calcium are also found in nerves, tissues, and all other parts. Calcium also helps in clotting blood and normalizing a person's heart beat. This may apply not only to humans but to all living things.
The answer would be that they are close to water hope this helps!
