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MHT-CET When the same monochromatic ray of light travels through water, the number of waves in glass slab of thickness 6 cm is same as in

water column of height  7 cm. If refractive index of water is

  1. 1.269

  2. 1.286

  3. 1.259

  4. 1.310

Answers (1)

It is given that wave number in 6cm of glass is the same as the wave number in water with height 7 cm.

Let \lambda _{g} is wavelength of light in glass and \lambda _{w}  is wavelength of light in water.

According to question, \frac{6}{\lambda _{g}} = \frac{7}{\lambda _{w}} \Rightarrow \frac{\lambda _{w}}{\lambda _{g}} = \frac{7}{6}

Also we know that relation between refractive index and wavelength, \frac{\mu _{g}}{\mu _{w}} = \frac{\lambda _{w}}{\lambda _{g}}

Putting values, \frac{1.5}{\mu _{w}} = \frac{7}{6} \Rightarrow \mu _{w} = 1.286

Option (2) is correct