Interference fringes from sodium light (λ = 5890 Å) in a double slit experiment have an angular width 0.20°, To increase the fringe width by 10%, new wavelength should be
Answer & explanation
Correct answer: option 4
$θ_1=\frac{λ_1}{d},\,θ_2=\frac{λ_2}{d}$
$∴\frac{θ_1}{θ_2}=\frac{λ_1}{λ_2}$ $∴λ_2=λ_1×\frac{θ_2}{θ_1}$
or $λ_2=5890×\frac{0.22}{0.20}=6479Å$