# AP Inter 2nd Year Physics Notes Chapter 2 Ray Optics and Optical Instruments

Students can go through AP Inter 2nd Year Physics Notes 2nd Lesson Ray Optics and Optical Instruments will help students in revising the entire concepts quickly.

## AP Inter 2nd Year Physics Notes 2nd Lesson Ray Optics and Optical Instruments

→ Light is form of energy which produces in us the sensation of light.

→ Optics is the study of visible light.

→ Reflection can take place on a smooth surface (or) on a rough surface like wall, floor etc.,

→ Mirage is an optical illustration generally observed in deserts.

→ Real images are always inverted and virtual images are always erect.

→ The image formed by a concave mirror cannot be beyond the focus.

→ In a concave mirror both f and R are taken as positive.

→ In a convex mirror both f and R are taken as negative.

→ Distances of real objects and real images are taken as negative.

→ Distances of virtual objects and virtual images are taken as positive.

→ Magnification produced by a mirror is negative when image formed is real.

→ Magnification produced by a mirror is positive when image formed is virtual.

→ Refractive index decreases with the increase in temperature.

→ Thicker the lens, lesser is its focal length.

→ Snell’s law fails, when light incident normally on a refracting medium.

→ Snells law states that the ratio of sine of angle of incidence to the sine of angle of refraction is equal to the refractive index of the medium.

→ The diameter of the mirror is called aperture of the mirror.

→ The middle point of the sphenical mirror is called its pole.

→ Principal axis is the line Joining the pole and the centre of curvature of the mirror.

→ The radius of the sphere, of which the mirror forms a part is called radius of curvature.

→ Focal length is the distance of the principal focus from the pole of mirror.

→ Power of a lens is the ability of a lens to converge (or) diverge the rays of light incident on it.

→ The spectrum of white light from the sun in the form of bows seen immediately after rain by an observer with his back towards the sun is called a rainbow.

→ The phenomenon of splitting up of white light into its constituent colours is called dispersion of light.

→ Myopia is a person can see near objects clearly and distinctly and distant objects are not clearly visible.

→ Hypermetropia is a person can see distant objects clearly and distinctly and near objects are not clearly visible.

Formulae

→ Focal length of concave mirror (f) = $$\frac{R}{2}$$

→ Mirror formula = $$\frac{1}{\mathrm{f}}=\frac{1}{\mathrm{u}}+\frac{1}{\mathrm{v}}$$

→ Linear magnification m = $$\frac{I}{o}=\frac{-v}{u}=\frac{f}{f-u}=\frac{f-v}{f}$$

→ Snells law $$\frac{\sin i}{\sin r}$$ = μ

→ Refractive index of a medium μ = $$\frac{c}{v}$$

→ μ = $$\frac{\mu_2}{\mu_1}$$, μ2 = $$\frac{1}{{ }_2 \mu_1}$$

→ μ = $$\frac{1}{\sin c}$$

→ $$\frac{-1}{\mathrm{u}}+\frac{\mu}{\mathrm{v}}=\frac{\mu-1}{\mathrm{R}}$$

→ Len’s makes formula $$\frac{1}{\mathrm{f}}=(\mu-1)\left(\frac{1}{\mathrm{R}_1}-\frac{1}{\mathrm{R}_2}\right)$$

→ Len’s formula, $$\frac{-1}{\mathrm{u}}+\frac{1}{\mathrm{v}}=\frac{1}{\mathrm{R}}$$

→ Linear magnification for a concave (or) convex lens
m = $$\frac{1}{O}=\frac{v}{u}=\frac{f}{f+u}=\frac{f-v}{f}$$

→ Power of a lens P = $$\frac{1}{f(\text { metre })}=\frac{100}{f(\text { centimetre })}$$

→ When two thin lenses are in contact $$\frac{1}{\mathrm{f}}=\frac{1}{\mathrm{f}_1}+\frac{1}{\mathrm{f}_2}$$

→ When two thin lenses are seperated by a distance $$\frac{1}{f}=\frac{1}{f_1}+\frac{1}{f_2}-\frac{d}{f_1 f_2}$$

→ Power of equivalent lens
p = p1 + p2 (In contact)
p = p1 + p2 – d p1p2 (seperated by a distance)

→ Refractive index (µ) = $$\frac{\sin \left(\frac{A+D_m}{2}\right)}{\sin A / 2}$$

→ Dispersive power (ω) = $$\frac{\delta_{\mathrm{v}}-\delta_{\mathrm{R}}}{\delta}=\frac{\mu_{\mathrm{v}}-\mu_{\mathrm{r}}}{\mu-1}$$

→ Magnifying power of a simple microscope m = 1 + $$\frac{\mathrm{D}}{\mathrm{f}}$$

→ Magnifying power of a compound microscope,
m = $$\frac{\mathrm{v}_0}{\mathrm{u}_0}\left(1+\frac{\mathrm{D}}{\mathrm{f}_{\mathrm{e}}}\right)=\frac{-\mathrm{L}}{\mathrm{f}_0}\left(1+\frac{\mathrm{D}}{\mathrm{f}_{\mathrm{e}}}\right)$$