The present invention relates to an exchangeable optical principles demonstrating kit. The kit includes a retractable sleeve structure having a first end and a second end; a grating plate including a grating film; and a pinhole plate including a pinhole opening, wherein the grating plate is selectively attached to the retractable sleeve structure by a magnetic connection, to render the exchangeable optical principles demonstrating kit to form an optical interference principle demonstrating device, and the pinhole plate is selectively attached to the retractable sleeve structure by a magnetic connection, to render the exchangeable optical principles demonstrating kit to form an optical pinhole principle demonstrating device.