Modeling seismic wave propagation and shadow zone

Objective:
Study of the path of seismic waves (refracted waves and reflected waves) to highlight the mantle/core boundary by observing shadow zones.

Principle:
The model consists of two concentric tanks containing liquids with different refractive indices: water is used for the mantle, glycerol for the core (easier to clean than oil).
The laser is fixed on a mobile device allowing to precisely change the beam angle using the graduated circle, without changing the entry point "the earthquake epicenter".
The reflected and refracted rays are easily observable inside the tanks with the addition of tracer dye, and shadow zones are clearly visible on the projection screen.
With the help of a transparent plate, the student can trace the path of the light beams representing seismic waves and identify shadow zones.
The third tank will allow testing a core of different size and illustrating the relationship between diameter and dimensions of the shadow zone.

Composition:
- Red laser source (650 nm) 1 mW (class II)
- 3 transparent tanks Ø 120 mm, 60 mm, and 45 mm
- Tank supports and laser source, with ball joint guidance
- White projection screen
- 2 transparent plates
- 30 ml of tracer dye for laser beam
Delivered with 2 AA type 1.5 V batteries