Maximum angle of diffraction in a plane transmission diffraction grating is:

Diffraction of light is the phenomenon of bending of light from the sharp corners of a slit or obstacle and spreading into the region of the geometrical shadow.

Diffraction can occur only when the wavelength of light is comparable to the size of the obstacle or the width of the slit.

Diffraction is of two types:

Fresnel Diffraction: It is the type of diffraction which occurs when the light source lies at a finite distance from the slit

Fraunhofer Diffraction: It is the type of diffraction which occurs when a plane wavefront is incident on the slit and the wavefront emerging from the slit is also plane.

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Plane Diffraction Grating:

1) A diffraction grating is an extremely useful device, and one of it consists of a large number of narrow slits side by side.

2) The slits are separated by opaque spaces.

3) When a wavefront is an incident on a grating surface, light is transmitted through the slits and obstructed by the opaque portions. Such a grating is called a transmission grating.

The formula for the diffraction grating is given by:

\(n\lambda = 2d Sinθ\)

Where,

n = Order of the spectrum,

d = distance between spectra,

θ = Angle, for maximum condition θ = 90° 

So, for the maximum angle of diffraction in a plane transmission diffraction grating is θ = 90° 

Additional Information

Francesco Grimaldi is credited for the discovery of the diffraction of light.

Diffraction: It is the spreading out of any wave due to an encounter with an obstacle.

Interference: It takes place when two or more electromagnetic waves combine to form another wave in which the displacement is either reinforced or cancelled.

Dispersion: Due to this phenomenon, white light is disintegrated into colours according to their wavelengths. 

Reflection: It is the change in the direction of any wave towards its original medium at an interface between the two mediums in which the wave is traversing.