Question

A beam of monochromatic blue light of wavelength 4200 Å in air travels in water $( \mu = 4 / 3 )$ . Its wavelength in water will be

• A. 2800 Å
• B. 5600 Å
• C. 3150 Å
• D. 4000 Å

Answer 1

Answer: (C)

3150 Å

Answer 2

$\frac { \mu _ { 1 } } { \mu _ { 2 } } = \frac { \lambda _ { 2 } } { \lambda _ { 1 } }$ $\Rightarrow$ $\frac { 1 } { 4 / 3 } = \frac { \lambda _ { 2 } } { 4200 }$

$\lambda _ { 2 } = 3150 \AA$