Question

A ray of light enters a rectangular glass slab of refractive index of 1.5. it is so found that 'the ray emerges from the opposite face of the slab without being displaced.it its speed is 3×10^8 ms^-1 then Whats its speed in the glass?

Answer 1

Rf= speed of light/ speed in vaccum or in given media

1.5=3×10^8/ speed in vaccum

Speed in vaccum= 3×10^8/1.5

Speed in vaccum= 2×10^8m/s^-1

Answer 2

Answer:

The speed of the light is 2 × 10⁸ m/s.

Explanation:

• The refractive index of a material is the measure of the bending of the light when it is passing from one medium to another medium.
• Sometimes it is also defined as the ratio between the sine of incidence angle to the sine of the refractive angle.

                                              $n = \frac{sin(i)}{sin(r)}$

• Refractive index is also explained by the given expression,

                                            $n=\frac{c}{v}$

where,

          n = refractive index

          c = speed of light in vacuum

          v = speed of light in medium

Here,

          n = 1.5

          c = 3 × 10⁸

                             $1.5 = \frac{c}{v}$

                       ∴     $v=\frac{c}{1.5}$

                              $v=\frac{3\times10^{8} }{1.5\\}$  

                         ∴   $v=2\times10^{8}$

Thus, the speed of light in the glass has a refractive index of 1.5 is 2 × 10⁸ m/s.