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# Tag Archives: Draft

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## Which way is better for giving AIEEE exam? ONLINE or OFFLINE.

Which way is better for giving AIEEE exam? ONLINE or OFFLINE.

I would personally recommend online. But the choice is up to you.

Please follow the following check to decide. Try to identify for yourself the plus points and negative points of writing AIEEE online and OFFLINE.

The most important disadvantage of choosing the OFFLINE version is the rarity of choices. You may have to travel long if you are not nearby the centre.

The decision is yours. But, think well before you decide.

## Does gravity travel instantaneously?

Does gravity travels instantaneously? Or it travels equal to the speed of light.

No clear answer now. If we believe in the Theory of relativity, Gravity (Gravitational Waves travel with the same speed as that of light in vacuum. If gravitons are like photons, then it makes sense too.

However I invite you to think more and post your thoughts as comments here. Let the discussion begin.

I found the following links to know more

• http://metaresearch.org/cosmology/speed_of_gravity.asp
• http://en.wikipedia.org/wiki/Speed_of_gravity
• http://www.desy.de/user/projects/Physics/Relativity/GR/grav_speed.html

## Numerical Problems From Optics

1. When an object of height 4cm is placed at 40cm from a mirror the mirror forms the image on the object itself. If the height of the image is equal to the height of the object. Find out the focal length of the mirror and identify the mirror.
2. A convergent beam of light passes through a diverging lens of focal length 0.2m and comes to focus at distance 0.3m behind the lens.Find the position of the point at which the beam would converge in the absence of lens?

## Speed of sound

Why sound travels faster in humid air than normal air as humid air is denser than normal air? (Akash asked)

The speed of sound in a medium is inversely proportional to the square root of its density. Humid air is less dense than dry air. Therefore the speed of sounf in humid air is greater than that in dry air.

Confused?

Are you thinking why dry air is more than that of humid air? This is a common misconception. Students used to think that humid air is denser than dry air. But it is not so. Just like skimmed milk (milk removed off its cream) is more dense than normal milk (with cream). Density of cream is much less than that of the rest of milk. So when it is removed, the residual milk becomes denser.

Humid air contains water vapor content. Water vapor is lighter than air. So when air contains water vapor, its density is less. When the water content is removed, it becomes denser.

For more details refer:

## What is present in between the atoms of gases?

What is present in between the atoms of gases?