A convergent meniscus lens is a lens that is composed of two spherical surfaces, like the on shown next:
The imaginary line that runs through the middle of the lens is the "symmetry axis".
In this type of lenses incident parallel beams of light converge in one point, as follows:
And thus we get the diagram.
When something is heated or cooled, its length changes by an amount proportional to the original length and the change in temperature: linear expansion : ΔL=αL0ΔT (α is the coefficient of linear expansion) The coefficient of linear expansion depends only on the material an object is made from.
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