Question

A triangular glass prism is able to produce spectrum when white light passes through it but a rectangular glass slab does not produce spectrum.give reason

Answer 1

a ray of light experiencing refraction in prism gets split into its constituent colors due to the fact that a ray of light consists of monochromatic lights of different wavelengths which have different speeds in a prism,refractive index depends upon the wavelength of the ray used{ cauchy's formula  μ=A+B/λ²+C/λ⁴+.... where A , B, C are the constants},

whereas when  a ray of light strikes the surface it does not split , just suffers a lateral displacement, due to the fact that the surfaces of the rectangular slab are parallel to each other and hence the different wavelenghts have to travel a common distance