Q83 / 90 · KVPY 2011 (SB/SX) · Physics
In a Young's double slit set-up, light from a laser source falls on a pair of very narrow slits separated by $1.0$ micrometer and bright fringes separated by $1.0$ millimeter are observed on a distant screen. If the frequency of the laser light is doubled, what will be the separation of the bright fringes ?
- A$0.25 \mathrm{~mm}$
- Correct answerB$0.5 \mathrm{~mm}$
- C$1.0 \mathrm{~mm}$
- D$2.0 \mathrm{~mm}$
Solution
Separation
$\begin{array}{l}
\text { Bright fringe }=\frac{\lambda D}{d} \\
f \lambda=c
\end{array}$
If $\mathrm{f}$ is doubled
$\lambda$ become halved
$\therefore \beta$ become half
$\beta=\frac{1}{2}=0.5 \mathrm{~mm}$
Hence, the correct answer is option: 'B'.