LIGHT EMITTING DIODE (LED)

    

     Now a days we often live without electronic light. Nearly this light can be emitted from a P-N junction operated as LIGHT EMITTING DIODE (LED).

                The LED is made up of p-n junction diode.

                                              HOW CAN A P-N JUNCTION GENERATE LIGHT???

     Consider  first a simple semiconductor. When an electron jump into a holes at the top of the valence band from the bottom of the conduction band, an energy E_g (equal to the gap width) is released. In silicon,

Why Spinning Ball Change Its Direction In Air?

 

The ball change its direction due to pressure difference in air(connect to ball) by the time of moving of the ball, will rotate about a particular axis of rotation.

Imagine a ball spinning about a vertical axis & moving in some velocity in horizontal direction   (in still air).

Let’s think the situation that, center of the ball is at rest and it spin in anticlockwise direction, about a vertical axis .The velocity of air is in opposite direction that of motion of the ball(as shown in the fig).