A point source of light S is placed in front of a perfectly...

A point source of light $S$ is placed in front of a perfectly reflecting mirror as shown in the figure. $S^{\prime}$ is a screen. The intensity at the centre of the screen is found to be $I$. If the mirror is removed then the intensity at the centre of the screen would be (a) $I$ (b) $\frac{10 I}{9}$ (c) $\frac{9 I}{10}$ (d) $2 I$

A point source of light $S$ is placed in front of a perfectly reflecting mirror as shown in the figure. $S^{\prime}$ is a screen. The intensity at the centre of the screen is found to be $I$. If the mirror is removed then the intensity at the centre of the screen would be
(a) $I$
(b) $\frac{10 I}{9}$
(c) $\frac{9 I}{10}$
(d) $2 I$

Key Concepts

Amplitude-Intensity Relationship

Light intensity is directly proportional to the square of its amplitude. When waves superpose constructively, their amplitudes add, and the resulting intensity is significantly altered. Understanding this relationship is key to predicting how interference from multiple sources will affect the observed brightness.

Superposition Principle

This principle states that when multiple waves overlap in space, the resultant displacement or amplitude at any point is the algebraic sum of the individual wave displacements. It is central to predicting the outcome of interference phenomena in optical systems.

Interference of Light

Interference occurs when two or more coherent light waves overlap, leading to regions of constructive and destructive interference. The intensity of the light at any point depends on the phase difference between the interacting waves, which in turn depends on the path difference and any phase changes upon reflection.

Image Method in Optics

The image method simplifies the analysis of systems with mirrors by replacing the mirror with a virtual image of the source. In this approach, the reflective surface is removed and the virtual source is treated as a real source, allowing one to study the interference or superposition of waves using straightforward geometry.

Reflection from a Mirror

This concept involves understanding how light behaves when it encounters a reflective surface. The angle of incidence equals the angle of reflection, and the reflected wave may undergo a phase shift depending on the reflecting medium. This phase change is crucial when analyzing interference effects created by the overlapping of incoming and reflected waves.

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