The transition zone between the crust and mantle is called as mohorovicic discontinuity.
The mohorovicic discontinuity was discovered by Andrija Mohorovicic in the year of 1909. The Moho lies at the depth of 35km beneath the continents and 8km beneath the oceanic crust. The Moho separates both the continental crust and the oceanic crust from underlying mantle. The Moho lies almost entirely within the lithosphere, only beneath the Mid Oceanic Ridge does it define lithosphere and asthenosphere boundary. Immediate above the Moho velocity of the P wave is 6km/sec and just below the Moho it becomes 8km/sec. Moho is characterised by up to 500km thick.
The Mohorovicic Discontinuity marks the lower limit of Earth's crust. It occurs at an average depth of about 8 kilometers beneath the ocean basins and 32 kilometers beneath continental surfaces. Mohorovicic was able to use his discovery to study thickness variations of the crust.
Mohorovicic discontinuity is the layer which is between the earth's crust and mantle. It's density ranges from 3.3 to 3.7.
When a ray of light travels into rarer medium from the denser medium and the angle of refraction is 90° so the angle of incidence in the denser medium is called critical angle for that pair of media.
Here, the angle of refraction is 90°, so the angle of incidence C is called the angle of incidence which is equal to the critical angle.
