| Obs # | Liquid Tested | Real Curvature $h_1 = R$ (cm) | Strip Surface $h_0$ (cm) | Apparent Curvature $h_2$ (cm) | Refractive Index $\mu = \frac{h_1 - h_0}{h_2 - h_0}$ | Parallax Check |
|---|---|---|---|---|---|---|
| No observations logged yet. Find $h_1$ and $h_2$, then click "Record to Observation Table". | ||||||
To find the refractive index of a liquid using a concave mirror and a plane mirror.
where:
• $h_1$ is the height of the needle tip from the pole of the dry concave mirror at its center of curvature $C$ ($R = h_1$).
• $h_0$ is the height of the plane mirror strip resting on the liquid surface from the mirror pole ($h_0 \approx 1.0\text{ cm}$, or $0$ for very thin layer).
• $h_2$ is the new coincidence height when rays refract through the liquid and reflect from the concave mirror.
If the liquid layer is very thin ($h_0 \approx 0$), the formula simplifies to:
When the needle tip is at height $h_2$, light rays entering the transparent liquid are refracted at the plane liquid surface toward the normal. If they strike the concave mirror normally along spherical radii, they reflect directly back along their incident paths. Upon re-emerging from the liquid surface into air, they refract back and re-converge to form an inverted real image coinciding tip-to-tip with the needle without parallax.