A travelling microscope, a glass slab, lycopodium powder/chalk dust, and a piece of paper are all required. A vertically mounted compound microscope is known as a travelling microscope. It has a vernier scale that may be moved up and down along with the main scale. The following is an experiment utilising a travelling microscope to determine the refractive index of a glass slab.
The refractive index is a measurement of how far a light ray deviates when it pauses between two materials. It’s a one-dimensional integer that determines the speed of light. The refractive index is defined as the ratio of light velocity. The numerator is the medium that is used to determine the refractive index. The denominator is the medium for which it is defined.
Three “glass slabs of varying thickness but made of the same material, a travelling microscope, and lycopodium powder A slab is a rectangular-shaped chunk of transparent material. All of the faces are transparent, and the faces on opposite sides are parallel. The thickness of a slab is the dimension along which light flows within it.
It’s a compound microscope with a vertical scale mounted on it. It has a Vernier scale that moves along the main scale and maybe pushed up and down. The reading is taken by combining the main scale and vernier scale readings in any position.
R1 without Glass Slab
| S. No. | M. S. R (cm) (a) | V. S. R. (cm) (b) | V. S. R LC (c) | (a + c) (cm) |
| 1 | 3.7 | 4 | 4 × 0.01=0.04 | 3.74 |
| 2 | 3.6 | 5 | 5 0.01=0.05 | 3.66 |
| 3 | 3.8 | 15 | 15 × 0.01=0.15 | 3.95 |
R2 with Glass Slab
| S. No. | M. S. R (cm) (a) | V. S. R. (cm) (b) | V. S. R LC (c) | (a + c) (cm) |
| 1 | 3.6 | 32 | 0.32 | 4.0 |
| 2 | 3.9 | 20 | 0.20 | 4.10 |
| 3 | 3.5 | 40 | 0.40 | 3.9 |
R3 with Lycopodium Powder on Glass Slab
| S. No. | M. S. R (cm) (a) | V. S. R. (cm) (b) | V. S. R LC (c) | (a + c) (cm) |
| 1 | 4.1 | 35 | 0.35 | 4.45 |
| 2 | 4.2 | 37 | 0.37 | 4.57 |
| 3 | 4.3 | 38 | 0.38 | 4.68 |
Mean value of R1 = 3.78 cm
Mean value of R2 = 4.0 cm
Mean value of R3 = 4.57 cm
Due to the phenomenon of refraction, when a glass slab is placed in air on a horizontal surface and its bottom side is viewed from above, it appears to be elevated. The apparent thickness of the slab is determined by the distance between the apparent bottom and the top surface of the slab. In a normal observation, the refractive index of glass with regard to the medium can be seen.
Also see:
| JEE Advanced | Standing waves |
| JEE Notification | Focal length of a convex lens |
| JEE Eligibility | pH scale |
| JEE Syllabus | Probability density |
| Equations of a parabola |
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