Figure 18. Parallel beams crossings or converging in the focus of the biconvex lens

From

The Experimental Teaching of the Conics Using the Reflection of the Light: The Conceptual Study of the Cassegrain Telescope

Juan Carlos Ruiz Mendoza

American Journal of Educational Research. 2019, 7(10), 699-707 doi:10.12691/education-7-10-5