Knowledge N Fact4u

How do tractor beams work ? •Up until recently, tractor beams (beams of light that tow objects) existed only in the world of science fiction. •While large-scale tractor beams that can tow space ships are still machines of the future, microscopic tractor beams are here today.  •The idea at first seams to defy physics. Shoot light at an object and the light's momentum should push the object away from the light source according to the law of conservation of momentum; not pull it closer like a tractor dragging its cargo. •But what if you managed to create a situation where upon striking the object, the light gains forward momentum instead of losing it.  •In that case, the law of conservation of momentum tells us that the object will lose momentum in the forward direction, even to the point of going backwards, towards the light source. •So there is a way to make a tractor beam without violating any physics, if you can get the light to ga...

Does the back of a rainbow look the same as its front side ? •A rainbow does not have a back side. If you were to walk completely to the other side of the mist cloud that is creating the rainbow and turn around, you would not see a rainbow.  •You have to realize that a rainbow is not a stationary physical object. Instead, it is a pattern of light that becomes a stable image only when you look at it from the right angle.  •You may not have noticed it, but every time you look directly at the center of a rainbow, the sun is directly behind your head. This is the only angle at which the light pattern that constitutes the rainbow can enter your eye and therefore lead you to see it. •The sun is always in the opposite part of the sky from the center of the rainbow. This is because a rainbow is actually just sunlight which has been refracted and reflected.  •Refraction occurs when the sunlight enters and leaves the small spherical water droplets that co...