Q. No.What will be the angular width of central maxima in Fraunhofer diffraction when the light of wavelength \(6000~\mathring {A}\) is used and slit width is \(12\times 10^{-5}~\text{cm}\)?
1. \(2~\text{rad}\)
2. \(3~\text{rad}\)
3. \(1~\text{rad}\)
4. \(8~\text{rad}\)
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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. |
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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. \(60^{\circ}\)
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| 1. | \(\theta\) increases. |
| 2. | \(\theta\) remains unchanged. |
| 3. | \(\theta\) decreases. |
| 4. | \(\theta\) increases or decreases depending on the intensity of light. |
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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. \(1.25\times 10^{-5}~\text{cm}\)
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Red light is generally used to observe diffraction patterns from a single slit. If the blue light is used instead of red light, then the diffraction pattern:
| 1. | will be clearer. |
| 2. | will contract. |
| 3. | will expand. |
| 4. | will not be visible. |
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The direction of the first secondary maximum in the Fraunhofer diffraction pattern at a single slit is given by:
\((a\) is the width of the slit)
1. \(a\sin\theta = \frac{\lambda}{2}\)
2. \(a\cos\theta = \frac{3\lambda}{2}\)
3. \(a\sin\theta = \lambda\)
4. \(a\sin\theta = \frac{3\lambda}{2}\)
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1. \(\sin^{-1}\frac{2}{3}\)
2. \(\sin^{-1}\frac{1}{2}\)
3. \(\sin^{-1}\frac{3}{4}\)
4. \(\sin^{-1}\frac{1}{4}\)
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1. \(\frac{\pi}{4}~\text{radian}\)
2. \(\frac{\pi}{2}~\text{radian}\)
3. \(\pi~\text{radian}\)
4. \(\frac{\pi}{8}~\text{radian}\)
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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. \(0.15~\text{cm}\)
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