Question

If N is the total number of rulings on the grating, n is the order of spectrum and λ is the wavelngth of light used, then resolving power of grating is given by

Answer 1

Answer:

where m is the order of the diffraction, λ is the wavelength of the diffracted light, d is the groove spacing of the grating, is the angle between the incident light and the grating normal, θί is the angle between the diffracted light and the grating normal.

Answer 2

Diffraction gratings are made either traditionally with a ruling engine and a diamond stylus burnishing grooves, or holographically using interference fringes formed at the junction of two laser beams1.

Planar or concave gratings having grooves that are parallel to one other are known as traditionally ruled gratings. In order to maximise system performance, holographic grating grooves might be either parallel or unequally distributed. Holographic gratings may be made on a variety of surfaces, including planar, spherical, toroidal, and many more.

Resolving “power” is given by:

Resolving power = $\frac{\alpha }{d\alpha }$

where, dα is the difference in wavelength between two spectral lines of equal intensity.

If the distance between two peaks is such that the maximum of one falls on the first minimum of the other, they are said to be resolved. The Rayleigh criteria is the name for this.

∴ R = nN

where N = total number of grooves or rulings.

n = order of spectrum