If you place two lenses consecutively, you can create a combined optical system. The overall behavior of the system depends on the properties of the individual lenses and their arrangement.
To create a converging lens using two lenses, you can use a positive (convex) lens followed by a negative (concave) lens. The positive lens converges light, bringing parallel rays toward a focal point, while the negative lens diverges light, spreading out parallel rays. By carefully selecting the focal lengths and positioning of the lenses, you can manipulate the behavior of the light to achieve convergence.
Here's what happens when you combine two lenses in this configuration:
Parallel rays: When parallel rays of light pass through the positive lens, they converge toward a focal point. However, after passing through the negative lens, they diverge again. The convergence of the positive lens and the subsequent divergence of the negative lens can cancel each other out, resulting in a beam that appears parallel after passing through both lenses.
Diverging rays: If you direct a diverging beam of light through the positive lens, it will be further diverged due to the converging nature of the lens. The negative lens, when placed after the positive lens, can partially reverse this divergence, causing the beam to become less divergent or even parallel again, depending on the specific lens parameters.
Overall, the net effect of combining the lenses depends on the focal lengths, positions, and relative orientations of the lenses. By carefully selecting these parameters, you can create a converging lens system using two lenses. However, it's important to note that combining lenses can introduce various aberrations and imperfections, which might affect the quality of the resulting converging beam. Optical design software or rigorous calculations are typically employed to optimize and simulate such setups for specific applications.