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# Tag Archives: Crafts

## Refraction – Disappearing letters

A rectangular block of glass is placed on a printed page lying on a horizontal table. what is the minimum value of u of glass so that the letters on page are not visible from any of the vertical faces of the block.

## Laws of motion – The problem of descending balloon.

A balloon is descending with a constant acceleration ‘a’ less than acceleration due to gravity. The mass of the balloon, with its basket and contents, is M. What mass m, of ballast(sand bags) should be released so that the balloon will begin to accelerate upward with constant acceleration ‘a’?

Posted by  Anisha Banerjee

## Problem from Ray Optics

A diverging beam of light from a point source S having divergence angle alpha falls symetricaally on a glass slab as shown in fig.The angles of incidence of the two extreme rays are equal.If the thickness of the glass slab is t and the refractive index is n,then the divergence angle of the emergent beam is,
a)0
b)alpha
c)sin inverse 1/n
d)2 sin inverse 1/n

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