# AP Inter 2nd Year Physics Notes Chapter 3 Wave Optics

Students can go through AP Inter 2nd Year Physics Notes 3rd Lesson Wave Optics will help students in revising the entire concepts quickly.

## AP Inter 2nd Year Physics Notes 3rd Lesson Wave Optics

→ Wave optics treats light as electromagnetic waves.

→ Wave front is the locus of all the points of a medium vibrating in the same phase.

→ Interference is non-uniform distribution of energy in the medium due to superposition of two light waves.

→ Two sources are said to be coherent, if they emit light of same frequency (or) wave length and a stable phase difference.

→ For constructive interference, the path difference between two sources should be an integral multiple of λ.

→ For destructive interference, the path difference between two sources should be an odd multiple of $$\frac{\lambda}{2}$$.

→ Dark and bright fringes are of same width in the interference pattern. → In Young’s double slit experiment, the fringes obtained are hyperbolic in shape.

→ The fringes obtained in Youngs’s double slit experiment appear straight in a small interference pattern.

→ Diffraction of light is the bending of light round the sharp comers and spreading into the regions of the geometrical shadow.

→ In a single slit diffraction pattern, all the secondary maxima and minima are of same width.

→ In a single slit diffraction pattern, the width of central maxima is twice the width of any other secondary maxima (or) minima.

→ The phenomenon of diffraction limits the resolving power of an optical instrument.

→ Polarisation is possible only in transverse waves.

→ Ordinary light from a source is unpolarised.

→ The phenomenon due to which vibrations of light are restricted in a particular plane is called Polarisation.

→ When a ray of light is incident at polarising angle, the reflected ray is at right angle to the refracted ray.

→ Fresnel distance is defined as the distance of the screen from the slit.

→ Limit of resolution is the smallest separation (linear (or) angular) between the two poiht objects, at which they appear just separated. → Resolving power is defined as the reciprocal of the limit of resolution.

→ The tangent value of Brewster’s angle is equal to the refractive index of the transparent medium, µ = Tan ip known as Brewster’s law.

→ Malus law states that the intensity of polarised light transmitted through the analyser varies as the square of cosine of the angle between the plane of transmission of analyser and polariser.
I ∝ cos2 θ

Formulae

→ Phase difference = $$\frac{2 \pi}{\lambda}$$ × path difference.

→ Condition for maximum intensity,
Φ = 2nπ.

→ Condition for minimum intensity,
Φ = (2n + 1)π.

→ Path difference S2P – S1P = nλ (maximum)
S2P – S2P (2n + 1) $$\frac{\lambda}{2}$$ (minimum).

→ Fresnel distance (ZF) = $$\frac{\mathrm{a}^2}{\lambda}$$

→ $$\frac{I_{\max }}{I_{\min }}=\frac{\left(a_1+a_2\right)^2}{\left(a_1-a_2\right)^2}$$

→ Position of Bright fringe xn = $$\frac{n \lambda D}{d}$$ → Position of dark fringe
xn = (2n + 1) $$\frac{\lambda \mathrm{D}}{\mathrm{d}}$$

→ Resolving power of Telescope
= $$\frac{1}{d \theta}=\frac{\mathrm{D}}{1.22 \lambda}$$

→ Resolving power of microscope
= $$\frac{1}{\mathrm{~d}}=\frac{2 \mu \sin \theta}{\lambda}$$

→Brewster’s law μ = Tan iB

→ Malus law I = I0 cos2 θ.