IIT JEE , AIEEE Forum - Fun Zone , General Knowledge

learner

Most of you would've done this as kids - hold a pencil at one end,gently, not hard and slowly shake it up and down.

The pencil appears to be curving, as though it was made of rubber.

Whats the explanation?

Thanks!:-)

rudra.panda

It is just optical illusion.

learner

Ok, but why does it take place??

spideyunlimited

Our eye's retina stores the image of what we see for some fraction of a second.... which is why we tend to imagine if the pencil is still there for some fraction of a second.. and a wavey effect is given rise to.
A housefly wouldn't notice any such effect.
Similarly we are able to see movies which are actually a certain number of frames per second. Other animals just see changing pictures.

learner

Ayt..yeah I remeber that...but why doesn't it happen if you hold it tight?

spideyunlimited

If you hold it tight, the pivot shifts more towards your hand, whereas if you leave it loose, the pivot point moves somewhere near the middle of the pencil which helps in this effect.

learner

Ok...thanks!!!:-)

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