Differentiate between Hertz and decibel.

Sheena recently went to a planetarium where she learnt about the universe and the celestial objects. Next, she enthusiastically narrated her experience to Reena. While doing so she also told her that recently an explosion took place on the moon and it was heard on the earth.

Do you think this is possible?

Two friends Rajesh and Rakesh were walking on the road on a moonlit night. Rajesh: I like to stare at the moon. It looks so peaceful. Rakesh: Yes, the moon is a quiet, comfortable place. I like the fact that there is no traffic on the moon and therefore, no sound pollution. Rajesh: Even the presence of traffic could not have caused noise pollution on the moon. Rakesh: Yes, that is true. The moon is smaller than the Earth and has much less gravity. So sound waves cannot travel on the moon and cause noise pollution. Rajesh: No, that is wrong! We know that sound waves cannot travel in vacuum and always need a medium. Since there is no air on the moon, sound cannot propagate on the moon.

Who is right—Rakesh or Rajesh?

Two friends Rajesh and Rakesh were walking on the road on a moonlit night. Rajesh: I like to stare at the moon. It looks so peaceful. Rakesh: Yes, the moon is a quiet, comfortable place. I like the fact that there is no traffic on the moon and therefore, no sound pollution. Rajesh: Even the presence of traffic could not have caused noise pollution on the moon. Rakesh: Yes, that is true. The moon is smaller than the Earth and has much less gravity. So sound waves cannot travel on the moon and cause noise pollution. Rajesh: No, that is wrong! We know that sound waves cannot travel in vacuum and always need a medium. Since there is no air on the moon, sound cannot propagate on the moon.

List three types of pollution not mentioned above.