Chemical, as the stuff/environment that is making it tarnish is a chemical reaction.
<u>Answer:</u> The spacing between the crystal planes is 
<u>Explanation:</u>
To calculate the spacing between the crystal planes, we use the equation given by Bragg, which is:
where,
n = order of diffraction = 2
= wavelength of the light = 
(Conversion factor: 
)
d = spacing between the crystal planes = ?
= angle of diffraction = 22.20°
Putting values in above equation, we get:
Hence, the spacing between the crystal planes is
The most common type of fluoride found in toothpaste is part of the compound sodium fluoride which has the chemical formula NaF
The tilt of the Earth's AXIS is the most important reason why seasons occur. We have hot summers and cold winters because of the tilt of the Earth's axis. The tilt of the Earth means the Earth will lean towards the Sun (Summer) or lean away from the Sun (Winter) 6 months later.
