Given below are two statements:
Statement I: A plane wave after passing through prism remains as plane wave but passing through small pin hole may become spherical wave.
Statement II: The curvature of a spherical wave emerging from a slit will increase for increasing slit wridth
In the light of the above statements, choose the correct answer from the options given below

We need to evaluate two statements about wave optics.

Statement I: "A plane wave after passing through a prism remains as a plane wave but passing through a small pinhole may become a spherical wave."

This is TRUE. A prism refracts a plane wave (changes its direction and introduces dispersion), but the wavefront remains essentially planar. However, when a plane wave passes through a small pinhole (whose size is comparable to the wavelength), diffraction occurs. The pinhole acts as a point source of secondary wavelets (by Huygens' principle), producing a diverging spherical wavefront.

Statement II: "The curvature of a spherical wave emerging from a slit will increase for increasing slit width."

This is FALSE. As the slit width increases, diffraction effects decrease. A wider slit allows the wave to pass through with less spreading, producing a wavefront that is closer to planar (less curved). Therefore, curvature decreases with increasing slit width, not increases.

The correct answer is Option (3): Statement I is true but Statement II is false.