pretty sure it's both are physical changes.
the pressure of the gas increases
Answer:
The process describes the source of energy of the Sun such that it shines as a result of nuclear fusion of hydrogen taking place.
Explanation:
The Sun generates energy by hydrogen within the Sun undergoing nuclear fusion to form helium.
Nuclear fusion reaction involves combining of two or more atomic nuclei to produce one or more completely different atomic nuclei as well as protons or neutrons, with a loss or gain of mass and the release or absorption of energy.
The process whereby four hydrogen atoms combine to form one helium atom with a mass deficit, which is accounted for by the release of energy, result in the high intense light of the Sun.
Doppler effect is the compression or extension of a sound wave, which causes a change in its wavelength / frequency (and so its sound).
Explanation: It is defined as the effect produced by a moving source of waves in which there is an upward shift in frequency for observers, the source is moving towards and downward shift of frequency from which the source is moving away. used to tell if an object in space is moving toward or away from us.
