Physics · Ch 9 — Ray Optics and Optical Instruments

Summary

Reflection of Light: Laws: incident, reflected, and normal lie in same plane; $\angle i = \angle r$ . For a plane mirror, image is virtual, erect, same size, and laterally inverted.
Spherical Mirrors: Focal length $f = \frac{R}{2}$ (concave: $f$ negative, convex: $f$ positive). Mirror equation: $\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$ . Magnification $m = -\frac{v}{u}$ .
Refraction: Snell’s law: $n_1 \sin i = n_2 \sin r$ . Absolute refractive index $n = \frac{c}{v}$ . Relative refractive index $n_{21} = \frac{n_2}{n_1}$ .
Lens Maker’s Formula: $\frac{1}{f} = (n-1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right)$ for a thin lens in air. Lens equation: $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$ . Magnification $m = \frac{v}{u}$ .
Power of Lens: $P = \frac{1}{f}$ (in metres), unit dioptre (D). For combination: $P = P_1 + P_2$ .
Total Internal Reflection: Occurs when light travels from denser to rarer medium and $i > i_c$ , where $\sin i_c = \frac{n_2}{n_1}$ . Applications: optical fibres, mirages.
Optical Instruments: Simple microscope: $M = \frac{D}{f}$ (final image at near point). Compound microscope: $M = \frac{L}{f_o} \cdot \frac{D}{f_e}$ . Astronomical telescope (normal adjustment): $M = \frac{f_o}{f_e}$ , length $L = f_o + f_e$ . …