Optics

Diffraction is the bending of light waves around obstacles or through openings, which occurs when light encounters an obstruction or a slit. This phenomenon results from the interference between different parts of the light wave. The pattern formed is a result of the constructive and destructive interference between the different parts of the light wave passing through or around the obstacle.
Key Concept: Diffraction is closely related to the interference of light waves. When two or more waves overlap, they combine to form a resultant wave, depending on whether they are in phase (constructive interference) or out of phase (destructive interference). This behavior is key to diffraction patterns.

Since the lens is silvered, it will act as a concave mirror, and the focal length becomes negative. The focal length of the mirror is . Using the mirror formula: where: - , - (since the object is 25 cm from the mirror), - is the image distance we need to find. Substitute the values: Solving for , we get: Thus, This means the image is formed 100 cm to the left of the system.

For the ray ST to be parallel to the incident ray PQ, the total change in the direction of the light must be zero after passing through all four media. The deviation of the ray at each interface is dependent on the refractive indices of the media. For the emergent ray to remain parallel to the incident ray, the refractive indices and must be equal.
Thus, , ensuring no net deviation of the light as it passes through the different media.