Answer:
enables us to understand those changes which no human being has ever seen (or if they have, they didn't record it) and to relate them to modern changes.
Expl
Answer:
D
the angles wich light is coming into the medium are not the same for all wavelengths (colors, at least in the visible spectrum). same for outgoing light.
the same it true for any transparent barrier between two different materials, like air and water.
The given statement is false.
The electrons have both wave and particles like properties. It was postulated by De Broglie that electrons have wave nature and suggested that all the matter exhibit wave characteristics. This concept is called the De Broglie hypothesis.
Like all the elementary particles, the electrons possess the characteristics of both waves and particles, in the sense that they can collide with other particles and be diffracted like light.
It's Bromine(Br-) Group 17 element that has 7 valence electrons on the fourth energy level.