Concave Lens
Purpose
Students observe that a concave (diverging) lens cannot form a real image on a screen, casting only a shadow. Holding the lens in front of your face shows students a reduced virtual image, illustrating the same principle used in eyeglasses that correct nearsightedness.
Figure 1:
The concave lens setup demonstrates how diverging lenses cast shadows rather than forming real images, as the refracted rays spread outward and never converge to a focal point.