Physics > Refraction of Light > 4.0 Thin lenses
Refraction of Light
1.0 Introduction
2.0 Laws of refraction
3.0 Apparent shift of an object
4.0 Thin lenses
4.1 Sign convention
4.2 Some important terms
4.3 Ray tracing
4.4 Image formed by covex lens
4.5 Image formed by concave lens
5.0 Lens makers formula & Other Functions of lens.
5.1 Thin Lens Formula
5.2 Magnification and Power of lens
5.3 Combination of lenses
5.4 Displacement method to find focal length.
5.5 Silvering of lens
6.0 Total internal reflection
7.0 Refraction through prism
8.0 Scattering of light
9.0 Optical instruments
9.1 Spectrometer
9.2 Simple microscope
9.3 Compound microscope
9.4 Astronomical telescope (Refracting type)
9.5 Terrestrial telescope
9.6 Galileo's terrestrial telescope
9.7 Reflecting type telescope
4.2 Some important terms
4.2 Some important terms
4.3 Ray tracing
4.4 Image formed by covex lens
4.5 Image formed by concave lens
5.2 Magnification and Power of lens
5.3 Combination of lenses
5.4 Displacement method to find focal length.
5.5 Silvering of lens
9.2 Simple microscope
9.3 Compound microscope
9.4 Astronomical telescope (Refracting type)
9.5 Terrestrial telescope
9.6 Galileo's terrestrial telescope
9.7 Reflecting type telescope
1. Principal axis: The line joining $C_1$ and $C_2$ is known as principal axis.
2. Centre of curvatures: $C_1$ and $C_2$ are centre of curvature of first and second refraction surface respectively. Also, $R_1$ and $R_2$ are their corresponding radius of curvature.
3. Optical centre: The centre $P$ of the thin lens which lies on the principal axis, is known as optical centre.
4. First focus $\left( {{F_1}} \right)$: It is defined as a point at which if an object is placed, the image of this object is formed at infinity.
Also, the rays passing through $F_1$ becomes parallel to the principal axis after refraction from the lens.
5. Second focus or principal focus $\left( {{F_2}} \right)$: A narrow beam of light travelling parallel to the principal axis either converge or diverge at point $F_2$ after refraction from the lens. This point $F_2$ is called as the second or principal focus.
If the rays converge at $F_2$, the lens is said to be converging lens and if they diverge, they are called as diverging lens.
