A light guide includes: a light guide board configured to allow light incident on an optical entrance to propagate through the light guide board, the light guide board including: the optical entrance; a first face; and at least one partial reflection layer within the light guide board and tilted to the first face. The at least one partial reflection layer is configured to reflect a part of light incident on the at least one partial reflection layer at an incident angle of greater than or equal to a critical angle θr to allow the reflected light to exit the light guide board through the first surface while transmitting therethrough a remainder of the light incident on the at least one partial reflection layer. Formula below is satisfied: θr=sin−1(n2/n1) where θr is the critical angle; n1 is a refractive index of the light guide board; and n2 is a refractive index of the at least one partial reflection layer.