Lay part of a newspaper on the desk. Lay the vial on the print. Try the vial side to side and then lay it top to bottom. Try raising the vial away from the print. Experiment with the water vial.
Lenses use refraction to magnify an object or to make it appear smaller.
Give each group a flashlight and a piece of poster board or construction paper. Prop the poster board against a wall. Have one student turn on the flashlight and stand one foot from the poster board with light focused on the center of the board. Have another student draw a square box around the area on the board where the light is most intense. Have the one holding the flashlight move back one foot and repeat the procedure.