Wave Optics Tes...

Two light rays having the same wavelength λ in vacuum are in phase initially. Then, the first ray travels a path L₁ through a medium of refractive index n₁ while the second ray travels a path of length L₂ through a medium of refractive index n₂. The two waves are then combined to produce interference. The phase difference between the two waves is

Using the expression 2d sin θ = λ, one calculates the value of d by measuring the corresponding angles θ in the range 0 to 90°. The wavelength λ is exactly known and the error in θ is constant for all values of θ. As, increases from 0°

The condition for diffraction of mth order minima is

Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure).

In Fraunhofer diffraction experiment, L is the distance between screen and the obstacle, b is the size of obstacle and λ is wavelength of incident light. The general condition for the applicability of raunhofer diffraction is

Following diffraction pattern was obtained using a diffraction grating using two different wavelengths λ₁ and λ₂. With the help of the figure identify which is the longer wavelength and their ratios?

In a Fraunhofer diffraction experiment at a single slit using a light of wavelength 400 nm, the first minimum is formed at an angle of 30°. The directipn θ of the first secondary maximum is given by