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 :
becomes narrower
goes horizontally without any deflection
bends downwards
bends upwards
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.
Study 40% syllabus and score up to 100% marks in JEE