Questions

6:45

Explanation: As you move from left to right, add 1 to the value of each digit on the watch, and rotate the digits one place to the left.

Because the refractive index of glass is highest, light travels slowly in Glass. 

We know that the speed of light depends on the refraction index. The higher the index of refraction is, the slower the speed of light is.

R.I of air and vacuum = 0 (air is a teeny bit more but can be taken as 0)
R.I of water = 1.33
R.I of glass = 1.4.

Hence, Light travels slowest in Glass.

Atomic  number  is  the  fundamental properties  of  an  element.  Every atom  is  identified  by  its  unique atomic  number.  Atomic  number  is equal  to  the  number  of  protons present in an atom of the element.