Dispersion of white light in a prism by wavelength and frequency

Steps:

• White light splits into spectrum due to varying refraction by wavelength.
• Visible spectrum ranges from red (longest wavelength, lowest frequency) to violet (shortest wavelength, highest frequency).
• Ends X and Y represent these extremes, with X as red and Y as violet.
• Thus, light at X has lower frequency than at Y.

Why B is correct:

• Frequency $f = c / \lambda$; red light (X) has longer $\lambda$, so lower $f$ than violet (Y).

Why the others are wrong:

• A: Speed varies with wavelength; violet slows more than red in prism glass.
• C: Violet (Y) refracts more than red (X) due to higher refractive index.
• D: Light refracts toward normal entering denser prism medium.

Final answer: B