An air bubble in a glass slab with refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and 3 cm deep when viewed from the opposite face. The thickness (in cm) of the slab is

  • Option 1)

    8

  • Option 2)

    10

  • Option 3)

    12

  • Option 4)

    16

 

Answers (1)

As we learnt in

Relation between real depth and apparent depth -

\frac{n_{i}}{d}= \frac{n_{r}}{d{}'}

 

- wherein

n_{i} = Refractive index of medium of incident.

n_{r} = Refractive index of medium of refraction.

d = distance of object.

d{}' = apparent  depth

 

 

Apparent depth=5cm  from one side 

\therefore Real depth=1.5x5=7.5 cm 

apparent depth=3cm from other side 

\therefore Real depth from other side =3x1.5cm=4.5

\therefore Thickness of slab=7.5cm+4.5cm=12cm

 


Option 1)

8

This option is incorrect 

Option 2)

10

This option is incorrect 

Option 3)

12

This option is correct 

Option 4)

16

This option is incorrect 

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