JEE PHYSICS MCQ: WAVE OPTICS

Solution approach

1. Correct Answer + Core Reason: $\frac{1}{2}{I_0}$. When unpolarized light passes through a polarizer, its intensity is halved.
   
   Step-by-Step Solution:
   
   Step 1: Recall the effect of a polarizing sheet on unpolarized light. A polarizing sheet only allows light waves with electric field vectors aligned along its polarization axis to pass through.
   
   Step 2: Consider the intensity of unpolarized light. Unpolarized light has electric field vectors oscillating in all directions.
   
   Step 3: Determine the intensity of the transmitted light. When unpolarized light passes through a polarizer, only half of the light (on average) is transmitted. Therefore, the intensity of the transmitted light is $\frac{1}{2}{I_0}$.
   
   Step 4: The question asks for the intensity of the light which does *not* get transmitted. This is the difference between the initial intensity and the transmitted intensity: ${I_0} - \frac{1}{2}{I_0} = \frac{1}{2}{I_0}$.
   
   Why other options are wrong:
   - Option A: Zero: This is incorrect because some light will always be transmitted (half of the initial intensity).
   - Option B: ${I_0}$: This is incorrect because the intensity is reduced after passing through the polarizing sheet.
   - Option D: $\frac{1}{4}{I_0}$: This is incorrect; the intensity is halved, not quartered.
   
   Key Concepts:
   - Polarization of light
   - Intensity of light
   - Malus's Law (for polarized light incident on a polarizer)
   
   Memory Aids:
   - Remember that unpolarized light passing through a polarizer has its intensity halved.
   
   Quick Tips:
   - Understand the difference between unpolarized and polarized light.