Question

A two slit Young's interference experiment is done with monochromatic light of wavelength 6000 A. The slits are 2 mm apart. The fringes are observed on a screen placed 10 cm away from the slits. Now a transparent plate of thickness 0.5 mm is placed in front of one of the slits and it is founded that the interference pattern shifts by 5 mm. The refractive index of the transparent plate is :

• A. $1.2$
• B. $0.6$
• C. $2.4$
• D. $1.5$

Answer 1

The correct option is A $1.2$

$(\mu -1)t=\frac{xd}{D}or\mu =1+\frac{xd}{Dt}$

$Or\mu =1+\frac{0.5\times 0.2}{10\times 0.05}=1+0.2=1.2$