Question

Students in a lab are trying to determine the wavelength of laser light by shining the laser through two narrow slits separated by $9.60$ micrometers toward a screen $4.00$ meters away. The first order bright fringes are $23.0$ centimeters from the center fringe.
What wavelength do the students determine?

• A. $680nm$
• B. $552nm$
• C. $883nm$
• D. $167nm$
• E. $8,832nm$

Answer 1

The correct option is B $552nm$

Given : $d=9.6$ $\mu m=9.6\times {10}^{-6}$ $m$ $D=4.00$ $m$ $y_1=23$ cm $=0.23$ m

Distance of first order bright fringe from central fringe, $y_1=\frac{\lambda D}{d}$

$\therefore$ $0.23=\frac{\lambda \times 4.00}{9.6\times {10}^{-6}}$

$⟹\lambda =0.552\times {10}^{-6}$ m $=552$ $nm$