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PHYSICS

PHYSICS With K K Sir

Light is form of energy which enables us to see the objects. We detect light with our eyes.

It’s mean eye is an optical instruments.

Question- How do we see the objects?

There are two types of the objects-

1) Luminous objects – Are those objects which have their own light.

Ex- Tube light, Bulb, CFL, LED light, SUN etc.

2) Non Luminous objects– Are those objects which do not have their own light.

Ex- Humen beings, Trees etc. 

QHow do we see the non luminous objects?

Ans- Non luminous objects reflect (or bounce back) some or all light falling on them.

Note: To see the objects there must be the presence of light.

Nature of Light

(1) Light  is a form of electromagnetic wave. 

      ⇒   It means light do not depends on any medium for its propagation.

      ⇒   Light can travel through any place – Solid, Liquid , Gas & can even through          Vacuum.

(2) Light always travel in straight line.

    ⇒  This property is called “RECTILINEAR PROPAGATION of LIGHT″.

(3) Speed of light is nearly 3 ×108 m/s in air or vacuum.

*  Electrostatics of Conductor (Behaviour of conductor in Electric field):

 1) Net Electric field inside the charged conductor is always ZERO why

     Reason:-  Suppose if E not equal to zero , then inside the conductor free electrons will experience  the force &  starts drifting opposite to the electric field direction.  And we have not achieved static condition yet. Means we are studying the static condition of charge but here when E.F applied the charge starts moving so due to that E.F inside the conduct always zero.

Even if conductor is placed inside the external electric field still Electric field inside the condutor will be zero.

2) Charge don’t resides on the outer surface of cavity inside the conductor.

3) What will happened when ever  isolated charge  (+q) placed inside the cavity of conductor ?

It mean what will be the charge on inner surface of cavity?

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