RAY TRACK APPARATUS (LSE) A compact visual teaching aid which is robust in construction wood board 400x280x13mm with matt white surface, mounted on rubber feet carries a circular scale with four quadrants 0 - 90? graduated every 2?, with two lines at right angles. The ray box is provided with slots to accommodate metal slits, colour filters, lenses etc., & is fitted with a 12V 24W line filament. Qty :