If we place a prism in a medium which has refractive index greater than that of prism then will dispersion take place ???

To address your question about whether dispersion occurs when a prism is placed in a medium with a higher refractive index than the prism itself, we need to delve into the concepts of refraction and dispersion. Dispersion is the phenomenon where different wavelengths of light are refracted by different amounts, leading to the separation of colors, as seen in a rainbow or when light passes through a prism.

Understanding Refraction and Dispersion

Refraction occurs when light travels from one medium to another and changes speed, which results in a change in direction. The amount of bending depends on the refractive indices of the two media involved. The refractive index (n) is a measure of how much light slows down in a medium compared to its speed in a vacuum. When light enters a medium with a higher refractive index, it slows down and bends towards the normal line (an imaginary line perpendicular to the surface at the point of incidence).

Conditions for Dispersion

Dispersion specifically refers to the separation of light into its constituent colors, which occurs due to the different degrees of refraction for different wavelengths. In a typical scenario, when white light enters a prism made of glass (which has a lower refractive index than air), the shorter wavelengths (blue and violet) are refracted more than the longer wavelengths (red and orange), resulting in a spectrum of colors.

What Happens in a Higher Refractive Index Medium?

Now, if we place a prism in a medium that has a higher refractive index than the prism itself, the situation changes significantly:

• Reduced Refraction: The light entering the prism from a medium with a higher refractive index will not bend towards the normal as it would in air. Instead, it may bend away from the normal, depending on the specific indices involved.
• Limited Dispersion: Since the light is already in a medium where it is slowed down more than in the prism, the differential refraction that causes dispersion is minimized. The light may not separate into its constituent colors effectively.
• Critical Angle Consideration: If the angle of incidence is greater than the critical angle for the prism-medium interface, total internal reflection could occur, preventing any light from exiting the prism and thus eliminating dispersion altogether.

Example to Illustrate the Concept

Imagine shining a white light beam into a glass prism while it is submerged in water (which has a higher refractive index than glass). Instead of seeing the familiar rainbow of colors, you might notice that the light does not disperse as expected. The water's refractive index causes the light to bend less when entering the prism, leading to minimal separation of colors.

Final Thoughts

In summary, placing a prism in a medium with a higher refractive index than the prism itself significantly alters the behavior of light. While refraction still occurs, the conditions necessary for effective dispersion are not met, resulting in little to no color separation. This illustrates the importance of understanding the interplay between different refractive indices in optical phenomena.