Dispersion and Scattering - UNSOLVED PRACTICE SET

Q7. What is dispersion of light? Name the colors in order of increasing deviation when white light passes through a prism.

Q8. Explain why violet light deviates more than red light when passing through a prism.

Q9. State Rayleigh's law of scattering. How does it explain the blue color of the sky?

Q10. Why does the sun appear red at sunrise and sunset but white at noon?

Q11. What is the difference between a pure spectrum and an impure spectrum? How is a pure spectrum produced in the laboratory?

Q12. Why are danger signals typically red in color? Explain using the concept of scattering.

Q13. Explain the phenomenon of dispersion of white light through a prism with a ray diagram. Why does the prism deviate different colors by different amounts?

Q14. State and explain Rayleigh's law of scattering. Use it to explain:

(a) The blue color of the sky

(b) The reddish appearance of the sun at sunrise and sunset

(c) Why clouds appear white

Q15. Describe an experiment to produce a pure spectrum in the laboratory. Draw the ray diagram and explain the role of each component.

Q16. The refractive indices of crown glass for red and violet light are 1.514 and 1.532 respectively. The angle of the prism is 6°.

(a) Calculate the angular dispersion produced by the prism.

(b) Calculate the mean deviation for yellow light (n_yellow = 1.523).

(c) Calculate the dispersive power of the prism material.

Q17. According to Rayleigh's law, the intensity of scattered light is inversely proportional to λ⁴.

(a) Calculate the ratio of scattering intensity for violet light (λ = 400 nm) to that for red light (λ = 700 nm).

(b) If the intensity of scattered blue light (λ = 450 nm) is I, what would be the intensity of scattered light of wavelength 900 nm for the same incident intensity?

(c) Explain why this wavelength dependence makes the sky appear blue rather than violet.

Q18. In your school's science fair, a student sets up an experiment to study dispersion using a prism and a white light source.

(a) She uses a prism with refracting angle 60°. For red light, the angle of minimum deviation is 38°. Calculate the refractive index for red light.

(b) For violet light in the same prism, the refractive index is 1.532. Calculate the angle of minimum deviation for violet light.

(c) The student then places a screen 2 m away from the prism to observe the spectrum. Calculate the approximate linear separation between the red and violet images on the screen if the angular separation is 1°.

(d) A classmate from a coastal town in Kerala mentions that during the monsoon, the sunsets are less red than in winter. Explain this observation using the concept of scattering and the presence of water droplets in the atmosphere.

(e) In India, many cities face severe air pollution. Explain how increased particulate matter in the air would affect the color of the sky and the visibility of distant objects.