Optics Ques 181
- The resolving power of electron microscope is higher than that of an optical microscope because the wavelength of electrons is …….. than the wavelength of visible light.
(1992, 1M)
Show Answer
Answer:
Correct Answer: 181.(d)
Solution:
Formula:
- In Young’s double slit experiment, the condition of bright fringe and dark fringe are,
for bright fringes (maxima), path difference $=n \lambda$
$$ d \sin \theta=n \lambda $$
for dark fringes (minima),
path-difference $=(2 n-1) \frac{\lambda}{2}$
$$ d \sin \theta=(2 n-1) \frac{\lambda}{2} $$
For the given question, distance between slits
$$ (d)=0.320 mm $$
Wavelength of light used $(\lambda)=500 n-m$
Angular range for bright fringe $(\theta)=-30^{\circ}$ to $30^{\circ}$
Hence, for bright-fringe,
$$ \begin{aligned} n \lambda & =d \sin \theta \\ n & =\frac{d \sin \theta}{\lambda}=\frac{0.320 \times 10^{-3} \times \sin 30^{\circ}}{500 \times 10^{-9}} \\ n _{\max } & =320 \end{aligned} $$
$\therefore$ Total number of maxima between the two lines are
Here, $n =\left(n _{\max } \times 2\right)+1$
$n n=(320 \times 2)+1 \ $
$n =641$
BETA
