Comets are like "dirty snowballs"; frozen gasses with dust and rocks in them. Each pass near the Sun causes the comet's nucleus to be exposed to intense sunlight, which causes some tiny fraction of the gas to evaporate and carry some of the dust and rock away into space. The gas and dust, near the Sun, cause the comet's "tail", and repeated passes cause dust and rock to spread out along most of the orbit of a comet. When the Earth enters one of these trails of old comet dust, we have meteor showers.
<span>On rare occasions, comets break apart or even more rarely, crash into planets. In 1994, the comet Shoemaker-Levy 9 broke apart and then collided with the planet Jupiter.</span>
Answer:
1. Reflection
2. travel from one medium to another
3. Same waves to travel in opposite direction.
Explanation:
1. When a wave strikes a solid barrier, it bounces back in the same medium. This wave behavior of bouncing back is known as reflection. Its like a basketball hitting a backboard. The ball bounces back at the same angle as it was incident. ∠i = ∠r
2. For refraction to occur in a wave, the wave must travel from one medium to another. When light travels from through mediums of different optical densities, it bends. The wave bends away normal when it enters from denser medium to rarer medium. The wave bends towards the normal when it enters from rarer to denser medium. The angle of refraction and angle of incidence are related by Snell's law.

3. The formation of standing wave requires two same waves to travel in the opposite direction and interfere. The incident wave and reflected wave when interfere, form standing waves. There waves are also resonances or harmonics. A standing wave oscillates at one place and does not transfers any energy.
I already said it but its reactivity
2Mg + 2HCl →2MgCl + 2H₂
Balanced is:
4Mg + 4HCl → 4MgCl + 2H₂
I Hope I Helped
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It is beacuse of fluid If there is no fluid, there is no drag. Drag is generated by the difference in velocity between the solid object and the fluid. If this statement is correct then how can there be drag in space if there is no air?