Concepts Of Physics MCQ Edition [Volume 1]PhysicsDispersion and Spectra
A narrow beam of white light passes through a slab that has parallel faces.
Options
- AThe light at no point splits into different colours.
- BThe emergent beam is white.
- CInside the slab, the light remains white.
- DInside the slab, the light separates into different colours.
Correct answer
D. Inside the slab, the light separates into different colours.
Step-by-step solution
When a narrow beam of white light enters a glass slab with parallel faces at an angle, it undergoes refraction at the first surface. The refractive index of the material varies for different wavelengths of light, causing different colours to refract at different angles. Thus, inside the slab, the white light separates into its constituent colours. Upon reaching the opposite parallel face, these separated colours refract again. Since the two faces of the slab are parallel, the emergent rays of all colours become par