Abstract: A lamp includes a base, a light emitting module mounted to the base, a lens member and a decorating unit. The lens member has a light input surface, a light output surface disposed in front of and spaced apart from the light input surface along an axis, and a through hole extending through the light input surface and the light output surface. Light emitted from the light emitting module enters the lens member through the light input surface and exits the lens member through the light output surface. The decorating unit is detachable and is optically disposed for decorating the lamp or for changing at least one of a wavelength, an output angle, a light field and so forth of the light passing through the lens member.