Affordable and effective! Quickly and easily demonstrate reflection, refraction and color mixing. Unique design includes adapters that fit on the end of each block to create a thin light beam that can be directed through optical blocks to study reflection, refraction and focal length. Arrange the beams to be parallel, diffused or convergent. Remove the adapters to create wider beams of light to show color mixing—blue + green + red = white light! A magnet is attached to the bottom so these versatile blocks can be used for classroom demonstrations on a whiteboard. 4½" x 1¼" x ¾".