Question

Young double-slit experiment is carried out by using green, red and blue light, one colour at a time. The fringe widths recorded are $\beta _{G}, \, \beta _{R}$ and $\beta _{B}$ respectively, then

• A. $\beta _{G}>\beta _{B}>\beta _{R}$
• B. $\beta _{B}>\beta _{G}>\beta _{R}$
• C. $\beta _{R}>\beta _{B}>\beta _{G}$
• D. $\beta _{R}>\beta _{G}>\beta _{B}$

Answer 1

Answer: (D)

Since, we know, fringe width,
$\beta =\frac{\lambda D}{d}$
Therefore, $\beta \propto \lambda $
Where, $\lambda =$ wavelength of light,
$D=$ distance between screen and slits
and $d=$ distance between slits.
We know, $\lambda _{R}>\lambda _{G}>\lambda _{B}$
Thus, $\beta _{R}>\beta _{G}>\beta _{B}$