Question

A beam of monochromatic blue light of wavelength 420 nm in air travels in water $(\mu =4/3)$. It wavelength in water will be

• A. 280 nm
• B. 560 nm
• C. 315 nm
• D. 400 nm

Answer 1

The correct option is C 315 nm

$v=\frac{c}{\mu }$ or ${\lambda }_m=\frac{{\lambda }_0}{\mu }$ $\therefore {\lambda }_m=\frac{420}{\left(4/3\right)}=315nm$