Lens Maker Equation Calculator
A lens is a transparent medium which is usually a glass bounded by two curved surfaces (generally spherical, cylindrical, or plane surfaces). There are two basic kinds of lenses: converging, and diverging. The focal length of a lens, which is usually denoted by âfâ, is defined as the distance between the optic centre and the focal point. The radius of curvature of the front surface is the distance between the optic centre and the point.
A lens may be permanently fixed to a camera, or it may be interchangeable with lenses of different focal lengths, apertures, and other properties. A converging lens brings all incident light-rays parallel to its optic axis together at a point, behind the lens, called the focal point, or focus, of the lens. A diverging lens spreads out all incident light-rays parallel to its optic axis so that they appear to diverge from a virtual focal point in front of the lens. Here, the front side of the lens is conventionally defined to be the side from which the light is incident.
Example:
Calculate the focal length of lens in air by the given details.
Radius of Curvature of the First Surface: 30
Radius of Curvature of the Second Surface: 40
Refractive Index of Lens Material: 50gmol/liter
Refractive Index of Ambient Medium: 10 kelvin
Solution:
Apply Formula:
1/f = (n_{1}/n_{m}-1) * (1/r_{1}-1/r_{2})
1/f = (50/10-1) * (1/30 - 1/40)
1/f = (50/9) * (0.0333 - 0.025)
1/f = (5.55)*(0.00833)
1/f = 0.0332
Focal Length: 0.0332