Question

Using Young’s double slit experiment, a monochromatic light of wavelength 5000 Å produces fringes of fringe width 0.5 mm. If another monochromatic light of wavelength 6000 Å is used and the separation between the slits is doubled, then the new fringe width will be

• A. 0.5 mm
• B. 1.0 mm
• C. 0.6 mm
• D. 0.3 mm

Answer 1

Answer: (D)

0.3 mm

Answer 2

The correct option is(D): 0.3 mm

Fringe width

$=\frac{λD}{d}$

$⇒Fringe\,Width \,∝ \frac{λ}{d}$

⇒ New fringe width

$⇒ 0.5\,mm×\frac{1.2}{2}=0.3\,mm$