Question

In a single slit diffraction experiment, the width of the slit is made double its original width. Then the central maximum of the diffraction pattern will become
(a) narrower and fainter
(b)narrower and brighter
(c)broader and fainter
(d) broader and brighter
The focal length of the objective and eye piece of a telescope are respectively 200 cm and 5 cm.
The maximum magnifying power of the telescope will be.

• A. -100
• B. -60
• C. -48
• D. -40

Answer 1

The correct option is C -48

As we know $\sin \theta =\frac{\lambda }{d}$

or, $\theta =\frac{1}{d}$.

Therefore, the diffraction pattern will become narrower and brighter.

Magnifying power is given by:

$f_e=5cm,f_o=200cm$

$M=-\frac{f_o}{f_e}(1+\frac{f_e}{d})$

Least distance of distinct vision, $d=25cm$

$M=-\frac{200}{5}(1+\frac{5}{25})M=-40\left(\frac{6}{5}\right)M=-48cm$