Question 98: Waves Optics

Question

The diffraction pattern of a light of wavelength $$400 \mathrm{~nm}$$ diffracting from a slit of width $$0.2 \mathrm{~mm}$$ is focused on the focal plane of a convex lens of focal length $$100 \mathrm{~cm}$$. The width of the $$1^{	ext {st }}$$ secondary maxima will be :

Accepted Answer

Width of $$1^{	ext {st }}$$ secondary maxima $$=\frac{\lambda}{a} \cdot D$$
Here
$$\begin{aligned}
& a=0.2 	imes 10^{-3} \mathrm{~m} \
& \lambda=400 	imes 10^{-9} \mathrm{~m} \
& D=100 	imes 10^{-2}
\end{aligned}$$
Width of $$1^{	ext {st }}$$ secondary maxima
$$\begin{aligned}
& =\frac{400 	imes 10^{-9}}{0.2 	imes 10^{-3}} 	imes 100 	imes 10^{-2} \
& =2 \mathrm{~mm}
\end{aligned}$$

Answer

2 mm

Answer

0.2 mm

Answer

0.02 mm

Answer

2 cm

Waves Optics

The diffraction pattern of a light of wavelength $400 \mathrm{~nm} diffracting from a slit of width 0.2 \mathrm{~mm} is focused on the focal plane of a convex lens of focal length 100 \mathrm{~cm}. The width of the 1^{\text {st }}$ secondary maxima will be :

Choose the correct answer: