A major breakthrough in the studies of cells came with the development of an electron microscope. This is because:

1.	the resolution power of the electron microscope is much higher than that of the light microscope.
2.	the resolving power of the electron microscope is 200-350 nm compared to 0.1-0.2 nm for the light microscope.
3.	electron beam can pass through thick materials, whereas light microscopy requires thin sections.
4.	the electron microscope is more powerful than the light microscope as it uses a beam of electrons that has a wavelength much longer than that of photons.

In a double-slit experiment, when the light of wavelength \(400~\text{nm}\) was used, the angular width of the first minima formed on a screen placed \(1~\text{m}\) away, was found to be \(0.2^{\circ}.\) What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water? \(\left(\mu_{\text{water}} = \dfrac{4}{3}\right)\)
1. \(0.1^{\circ}\)
2. \(0.266^{\circ}\)
3. \(0.15^{\circ}\)
4. \(0.05^{\circ}\)

Two periodic waves of intensities I₁ and I₂ pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is:

1.  $2\left({\mathrm{l}}_1+{\mathrm{l}}_2\right)$

2.  ${\left({\sqrt{\mathrm{I}}}_1+{\sqrt{\mathrm{l}}}_2\right)}^2$

3.  ${\left({\sqrt{\mathrm{I}}}_1-{\sqrt{\mathrm{l}}}_2\right)}^2$

4.  $2\left({\sqrt{\mathrm{I}}}_1-{\sqrt{\mathrm{l}}}_2\right)$

For a parallel beam of monochromatic light of wavelength \(\lambda\), diffraction is produced by a single slit whose width \(a\) is much greater than the wavelength of the light. If \(D\) is the distance of the screen from the slit, the width of the central maxima will be:

In Young's double-slit experiment, the separation \(d\) between the slits is \(2~\text{mm}\), the wavelength \(\lambda\) of the light used is \(5896~\mathring{A}\) and distance \(D\) between the screen and slits is \(100~\text{cm}\). It is found that the angular width of the fringes is \(0.20^{\circ}\). To increase the fringe angular width to \(0.21^{\circ}\) (with same \(\lambda\) and \(D\)) the separation between the slits needs to be changed to:
1. \(1.8~\text{mm}\)
2. \(1.9~\text{mm}\)
3. \(2.1~\text{mm}\)
4. \(1.7~\text{mm}\)

In Young's double-slit experiment, if there is no initial phase difference between the light from the two slits, a point on the screen corresponding to the fifth minimum has a path difference:

The angular width of the central maximum in the Fraunhofer diffraction for \(\lambda=6000~{\mathring{A}}\) is \(\theta_0\). When the same slit is illuminated by another monochromatic light, the angular width decreases by \(30\%\). The wavelength of this light is:
1. \(1800~{\mathring{A}}\)
2. \(4200~{\mathring{A}}\)
3. \(420~{\mathring{A}}\)
4. \(6000~{\mathring{A}}\)