Direction : The question has a paragraph followed by two statements, Statement-1 and Statement-2. Of the given four alternatives after the statements, choose the one that describes the statements.

A thin air film is formed by putting the convex surface of a plane-convex lens over a plane glass plate. With monochromatic light, this film gives an interference pattern due to light reflected from the top (convex) surface and the bottom (glass plate) surface of the film.

Statement - 1: When light reflects from the air- glass plate interface, the reflected wave suffers a phase change of \pi.

Statement - 2: The centre of the interference pattern is dark.

 

  • Option 1)

    Statement-1 is true, Statement-2 is false.

  • Option 2)

    Statement-1 is true , Statement-2 is true, Statement-2 is the correct explanation of Statement-1.

  • Option 3)

    Statement-1 is true, Statement-2 is true, Statement-2 is not the correct explanation of Statement-1.

  • Option 4)

    Statement-1 is false, Statement-2 is true.

 

Answers (1)
P Prateek Shrivastava

As we learnt in

Relation between angle of incidence and angle of refaction -

\mu _{1}\sin i= \mu _{2}\sin r
 

- wherein

\mu _{1}= refractive index of medium of incidence.

\mu _{2}=  refractive index of medium where rays is refracted.

i= angle of incidence.

r= angle of refraction.

 

 

Thin lens formula -

\frac{1}{v}-\frac{1}{u}= \frac{1}{f}

 

- wherein

u \, and \, v are object and image distance from lens.

 

S1= When light reflects from denser (glass) a phase drift of \pi is generated.

S2= Centre maximum or minima depends on thickness of the lens. 

Correct option is 3.

 


Option 1)

Statement-1 is true, Statement-2 is false.

This is an incorrect option.

Option 2)

Statement-1 is true , Statement-2 is true, Statement-2 is the correct explanation of Statement-1.

This is an incorrect option.

Option 3)

Statement-1 is true, Statement-2 is true, Statement-2 is not the correct explanation of Statement-1.

This is the correct option.

Option 4)

Statement-1 is false, Statement-2 is true.

This is an incorrect option.

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