Diffraction pattern cannot be observed with one wide slit.



Diffraction is a phenomenon that occurs when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. It results in the bending and spreading of the wave around the edges of the obstacle or slit, creating a pattern of light and dark regions known as a diffraction pattern.

In order to observe a diffraction pattern, the following conditions must be met:

1. Coherent Light Source: The light source used should be coherent, meaning that the waves emitted from different parts of the source have a constant phase relationship. Examples of coherent light sources include lasers.

2. Narrow Slits: The width of the slit should be comparable to the wavelength of the light. This allows for the bending and spreading of the wave around the edges of the slit.

3. Monochromatic Light: The light used should consist of a single wavelength or color. This ensures that the diffraction pattern is not blurred by the presence of multiple wavelengths.

With these conditions in mind, let's analyze the given options:

- One wide slit: When a wide slit is used, the width of the slit is much larger compared to the wavelength of the light. As a result, the bending and spreading of the wave around the edges of the slit are negligible. This means that the conditions for diffraction are not met, and hence no diffraction pattern can be observed.

- Two narrow slits: Two narrow slits would create an interference pattern rather than a diffraction pattern. Interference occurs when two or more waves overlap and combine, resulting in constructive and destructive interference. This pattern can be observed when two coherent light sources are used, such as in the famous Young's double-slit experiment.

- One narrow slit: A single narrow slit can produce a clear diffraction pattern. This is a well-known phenomenon known as single-slit diffraction.

- Large number of narrow slits: A large number of narrow slits arranged close together would create a diffraction grating, which produces a more complex diffraction pattern compared to a single-slit diffraction.

In conclusion, the correct answer is option 'A' - diffraction pattern cannot be observed with one wide slit because the width of the slit is too large compared to the wavelength of the light.