Even 6: Determination of refractive Index of a material of glass slab.

 Aim: Determination of refractive Index of a material of glass slab.

Apperatus : glass slab ,ruler,chalk,pencil, traveling microscope

Formula : 

n = real depth / apperant depth

Diagram : 

Prcedure : 

The principle:When a glass slab is placed on a horizontal surface, and its bottom surface is viewed from the top, due to refraction, it appears to be elevated. The apparent thickness of the slab is determined from the distance between the apparent bottom and the top of the glass slab. 

1. Here first observe the ink dot without glass slab with the help of traveling microscope focus the image with the help of vertical scale.

2.calculate the real depth of glass slab i.e thickness. Put a glass slab on that ink dot and see that the dot is appearing near to the eyepiece than the original position. Note down the reading from traveling microscope.

3. Calculate the real and apparent depth as shown in fig 1. Calculate the RI of glass slab from formula.

Result: 

The ratio R3−R1R3−R2 is constant and gives the refractive index of the glass slab. Calculated as RI=1.5

Precautions

1. The parallax in a microscope should be removed properly.
2. To avoid backlash error, the microscope should be moved upward.

n=realthicknessoftheslabapparentthicknessoftheslab