The invention provides a demonstration instrument for demonstrating
optical refraction and reflection law and measuring index of
refraction on a blackboard. The demonstration instrument is composed ofa projection
laser pen,
laser pen placing and inserting parts, adjusting parts, a
lantern ring, a T-shaped support plate, a cylinder-shaped rack, a gear sliding platform
assembly, a connecting rod, an arc-shaped sliding chute, magnetic suckers, a Y-shaped bottom plate, an optical element, a scale disk, studs, gaskets, second springs, butterfly nuts, fixing parts and the like. Based on the technology of the invention with the application number 2019105819888, the technical scheme is characterized in that a gear is mounted at one end of a Pi-shaped sliding platform, the rack is formed in the bottom of the arc-shaped sliding chute, the Pi-shaped sliding platform is driven to move on the arc-shaped sliding chute by utilizing tooth
coupling, the tiny adjustment for the incidence angle of incident rays is realized, the springs are arranged between the scale disk and the Y-shaped bottom plate for supporting, so that the direction of the face of the scale disk can be conveniently adjusted, the Y-shaped bottom plate and the arc-shaped sliding chute are connected to form a whole, so that the requirement for the
hardness of a manufacturing material is reduced, the manufacturing cost and difficulty are reduced, the adjustment for the incident rays and the face of the scale disk is facilitated, time is further saved, and the classroom teaching efficiency is improved.