On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens’ principle leads us to conclude that as it travels, the light beam :

  • Option 1)

     becomes narrower
     

     

  • Option 2)

    goes horizontally without any deflection

  • Option 3)

     bends downwards

     

  • Option 4)

    bends upwards

 

Answers (1)
A Aadil

As we learnt in

Coherent Source -

If they produce wave of same frequency with a constant phase different.

- wherein

Necessary condition to observe interference.

 

 Consider a plane wavefront travelling horizontally. As refractive index of air increases with height. So speed of wavefront decreases with height. Hence the light beam bonds upwards.

Correct option is 4.

 


Option 1)

 becomes narrower
 

 

This is an incorrect option.

Option 2)

goes horizontally without any deflection

This is an incorrect option.

Option 3)

 bends downwards

 

This is an incorrect option.

Option 4)

bends upwards

This is the correct option.

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