Q. No.A diffraction pattern is observed using a beam of red light. What will happen if the red light is replaced by the blue light?
| 1. | No change takes place. |
| 2. | Diffraction bands become narrower. |
| 3. | Diffraction bands become broader. |
| 4. | Diffraction pattern disappears. |
The first diffraction minima due to a single slit diffraction is at \(\theta = 30^{\circ}\) for a light of wavelength \(5000~\mathring {A}.\) The width of the slit is:
1. \(5\times 10^{-5}~\text{cm}\)
2. \(10\times 10^{-5}~\text{cm}\)
3. \(2.5\times 10^{-5}~\text{cm}\)
4. \(1.25\times 10^{-5}~\text{cm}\)
A parallel beam of monochromatic light of wavelength \(5000~\mathring{A}\) is incident normally on a single narrow slit of width \(0.001\) mm. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to:
1. \(0^{\circ}\)
2. \(15^{\circ}\)
3. \(30^{\circ}\)
4. \(60^{\circ}\)
1. \(\sin^{-1}\frac{2}{3}\)
2. \(\sin^{-1}\frac{1}{2}\)
3. \(\sin^{-1}\frac{3}{4}\)
4. \(\sin^{-1}\frac{1}{4}\)
1. \(3~\text{mm}\)
2. \(9~\text{mm}\)
3. \(4.5~\text{mm}\)
4. \(1.5~\text{mm}\)
| 1. | The diffraction pattern is not observed on the screen in the case of electrons. |
| 2. | The angular width of the central maximum of the diffraction pattern will increase. |
| 3. | The angular width of the central maximum will decrease. |
| 4. | The angular width of the central maximum will remain the same. |
A linear aperture whose width is \(0.02\) cm is placed immediately in front of a lens of focal length \(60\) cm. The aperture is illuminated normally by a parallel beam of wavelength \(5\times 10^{-5}\) cm. The distance of the first dark band of the diffraction pattern from the center of the screen is:
1. \(0.10~\text{cm}\)
2. \(0.25~\text{cm}\)
3. \(0.20~\text{cm}\)
4. \(0.15~\text{cm}\)
1. \(\frac{\pi}{4}~\text{radian}\)
2. \(\frac{\pi}{2}~\text{radian}\)
3. \(\pi~\text{radian}\)
4. \(\frac{\pi}{8}~\text{radian}\)
A beam of light of \(\lambda = 600~\text{nm}\) from a distant source falls on a single slit \(1~\text{mm}\) wide and the resulting diffraction pattern is observed on a screen \(2~\text{m}\) away. The distance between the first dark fringes on either side of the central bright fringe is:
1. \(1.2~\text{cm}\)
2. \(1.2~\text{mm}\)
3. \(2.4~\text{cm}\)
4. \(2.4~\text{mm}\)
| 1. | \(2 \pi\) | 2. | \(3 \pi\) |
| 3. | \(4 \pi\) | 4. | \( \pi \lambda\) |
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