Question

In young's double slit experiment a glass plate of refractive index 1.5 and thickness 5 x 10^-4 cm is kept in the path of one of the light rays ,then the optical path of the ray will be increase by 2.5 × 10^-4 cm. Explain how

Answer 1

solution :a/c to question, a glass plate of refractive index 1.5 is kept in the part of one of light rays .

optical path length is given by, x=$\frac{yd}{D}+(\mu-1)t$

here it is clearly shown that, path length is increased by $(\mu-1)t$

where, $\mu$ is refractive index of glass plate and t is thickness of glass plate.

here, $\mu$ = 1.5 and t = 5 × 10^-4 cm

now, increase path length = (1.5 - 1) × 5 × 10^-4 cm

= 0.5 × 5 × 10^-4 cm

= 2.5 × 10^-4 cm

hence, path length is increased by 2.5 × 10^-4 cm