MCQ
A slit of width $a$ is illuminated by white light. For red light ($\lambda = 6500 \;\mathring A$), the first minima is obtained at $\theta = {30^o}$. Then the value of $a$ will be
- A$3250 Å$
- B$6.5 \times {10^{ - 4}}mm$
- ✓$1.24\; microns$
- D$2.6 \times {10^{ - 4}}cm$
