Question 242: Waves Optics

Question

In a biprism experiment a steady interference pattern is observed on the screen using a light of wavelength $5000 \mathop {\rm{A}}\limits^{\rm{o}}$. Without disturbing the set up of the experiment, the source of light is replaced by a source of wavelength $6400 \mathop {\rm{A}}\limits^{\rm{o}}$.
The fringe width will

Accepted Answer

$$ \begin{aligned} &\begin{aligned} & \mathrm{W}=\frac{\lambda \mathrm{D}}{\mathrm{~d}} \ 	herefore & \frac{\mathrm{~W}_1}{\mathrm{~W}_2}=\frac{\lambda_1}{\lambda_2} \ 	herefore & \frac{\mathrm{~W}_2-\mathrm{W}_1}{\mathrm{~W}_1}=\frac{\lambda_2-\lambda_1}{\lambda_1}=\frac{6400-5000}{5000}=\frac{1400}{5000} \ &\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, =\frac{7}{25}=0.28=28 \% \end{aligned}\ &	ext { Therefore, the fringe width will increase by } 28 \% 	ext {. } \end{aligned} $$

Answer

decrease by $48 \%$

Answer

decrease by $28 \%$

Answer

increase by $48 \%$

Answer

increase by $28 \%$

Waves Optics

Choose the correct answer: