Galaxy Formation. One says that galaxies were born when vast clouds of gas and dust collapsed under their own gravitational pull, allowing stars to form. The other, which has gained strength in recent years, says the young universe contained many small "lumps" of matter, which clumped together to form galaxies.
I believe Mendeleev formed his periodic table by atomic weight (nowadays we do it by atomic number) so he likely used those values.
Answer: The answer is C
Explanation: Sound waves tend to spread farther the deeper the sound is, and the waves go lower then the second example, deeming it is louder.
Answer:
The transition from lower energy level to higher energy level require a gain of energy.
Explanation:
When transition occur from lower energy level to higher energy level require a gain of energy. Electron could not jump unto higher energy level without gaining thew energy.
When electron jump into lower energy level from high energy level it loses the energy.
For example electron when jumped from 2nd to 3rd shell it gain energy and when in return back to 2nd shell from 3rd shell it loses energy.
The process is called excitation and de-excitation.
Excitation:
When the energy is provided to the atom the electrons by absorbing the energy jump to the higher energy levels. This process is called excitation. The amount of energy absorbed by the electron is exactly equal to the energy difference of orbits.
De-excitation:
When the excited electron fall back to the lower energy levels the energy is released in the form of radiations. this energy is exactly equal to the energy difference between the orbits. The characteristics bright colors are due to the these emitted radiations. These emitted radiations can be seen if they are fall in the visible region of spectrum.
From shortest wavelength to longest wavelength: ultraviolet ,visible light ,infrared
