Converging Lens Model - Optics Step by Step

A converging lens takes incoming parallel rays and bends them toward a common focal point.

optics The thin-lens drawing is an idealized model. It keeps the useful ray geometry and scopes out thick-lens details.

Example

A converging lens takes incoming parallel rays and bends them toward a common focal point. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Start with parallel rays

A converging lens has a simple model rule: rays that arrive parallel to the axis bend toward one common point on the far side of the lens.

\text{parallel in} \Rightarrow \text{bend toward focus}

The rays meet at the focus

The focus is not a label chosen after the fact. In the model diagram, the bent rays go through the same point. That point is the focus of the converging lens.

\text{focus} = \text{where parallel rays meet}

Both drawn rays name the same point

The top ray and bottom ray arrive at different heights, but after the lens they are aimed at the same focus. That shared point is the structural claim of this simple converging-lens diagram.

\text{top ray focus}=\text{bottom ray focus}