Consider sunlight incident on a pinhole of width \(10^{3}~\mathring{{A}}\). The image of the pinhole seen on a screen shall be:
| (a) | a sharp white ring |
| (b) | different from a geometrical image |
| (c) | a diffused central spot, white in colour |
| (d) | diffused coloured region around a sharp central white spot |
Choose the correct option from the given ones:
| 1. | (a) and (c) only |
| 2. | (a) and (d) only |
| 3. | (b) and (d) only |
| 4. | (b) and (c) only |
Step: Analyse each statement one by one.
The width of the pinhole is given as \(10^{3}~\mathring{A}= 100~\text{nm}\). This is comparable to the wavelength of visible light (approximately \(400\text-700~\text{nm}\)).
When light passes through such a small aperture, diffraction occurs, and the observed image is not a sharp geometric shadow but rather a diffraction pattern. This pattern typically consists of a central bright spot (white in this case, as sunlight contains all colors) surrounded by diffused colored fringes due to wavelength-dependent diffraction effects.
Therefore, the image of the pinhole is different from a geometrical image and a diffuse central spot, white in colour.
Hence, option (3) is the correct answer.
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