Why is air invisible ?

Air does affect light,but not much,so it seems invisible.First reason is that the average air molecule is about 1 nm across,while light waves are on the order of 500 nm across. Hence,light continues its way not being affected.Another reason is that atoms are widely spaced where light pass through, since it has a small chance of interacting with air .However,if there is a lot of air,light can affect molecules in a phenomenon called “scattering “ later we will discuss it in the question ‘Why is the sky blue ?’

Why compass needle always points North ?

The Earth has its own magnetic field , it acts like there is huge bar magnet buried inside,but this bar magnet is not on the earth rotational axis it is shifted by some angle.The south of the bar magnet is on the magnetic north and the south polarity is on the magnetic north(image).As opposite polarities attract the magnetic needle (north) is attracted to the south polarity in the magnetic north.That’s why the needle always points north.If you want to know “why earth has magnetic field?”go to letter E.

Why Roads Are Black in Colour ?

There are reasons for why roads are black in colour that I identified and I want to share with you :- Asphalt concrete is available at a low price. The cost that occurs to made of asphalt roads is also low. During the summer and high temperatures, the black color does not reflect the solar waves that will help us to see the roads clearly. Asphalt concrete absorbs heat but that doesn’t affect visibility in extremely hot conditions. In night times bright colors can be easily seen on black roads. whereas bright colors on white roads cannot easily be identified. We can easily say that white lines can be easily identified on black roads whereas white line road markings cannot be identified easily on the white roads. In addition, any irregularity on the road, with the exception of the black color, can be simply detected.

Why do objects of different masses reach ground at same time ?

Before Galileo it was thought that heavy object weighs more.So it must fall down,since it has more weight (greater downward force applied to it). But that was proved wrong when Galileo threw two balls of different masses from Pisa tower.Where the heavier object get more mass that means it gets more inertia (more resistive to move).Hence,it needs more gravitational force (weight) to accelerate it at the same rate as the light one.

Physistri

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