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 = \(\frac{\mu_2}{\mu_1}\), μ_{2} = \(\frac{1}{{ }_2 \mu_1}\)

→ 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 = p_{1} + p_{2} (In contact)

p = p_{1} + p_{2} – d p_{1}p_{2} (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 = \(\frac{\mathrm{v}_0}{\mathrm{u}_0}\left(1+\frac{\mathrm{D}}{\mathrm{f}_{\mathrm{e}}}\right)=\frac{-\mathrm{L}}{\mathrm{f}_0}\left(1+\frac{\mathrm{D}}{\mathrm{f}_{\mathrm{e}}}\right)\)