A ray of light is incident at an angle of incidence \( 60^\circ \) on the glass slab of refractive index \( \sqrt{3} \). After refraction, the light ray emerges out from other parallel faces and lateral shift between incident ray and emergent ray is \( 4\sqrt{3} \, \text{cm} \). The thickness of the glass slab is ________ \( \text{cm} \).