When ordinary light is made incident on a quarter wave plate, the emergent light is

Options

A. linearly polarised
B. circularly polarised
C. unpolarised
D. elliptically polarised

Answer

To solve the question regarding the behavior of ordinary light when it passes through a quarter wave plate, we can follow these steps:

### Step 1: Understand the Concept of a Quarter Wave Plate
A quarter wave plate is an optical device that introduces a phase difference of 90 degrees (or a quarter wavelength) between two orthogonal components of light. It is primarily used to manipulate the polarization state of light.

**Hint:** Remember that a quarter wave plate can convert linearly polarized light into circularly polarized light or vice versa, depending on the orientation of the light with respect to the plate.

### Step 2: Identify the Nature of Ordinary Light
Ordinary light, such as white light, is unpolarized, meaning it consists of light waves vibrating in multiple planes. When this unpolarized light passes through a quarter wave plate, the plate interacts differently with the components of light.

**Hint:** Consider how unpolarized light is composed of various polarization states and how a quarter wave plate affects these states.

### Step 3: Analyze the Effect of the Quarter Wave Plate
When unpolarized light passes through a quarter wave plate, the plate separates the light into two orthogonal components: one that travels faster and one that travels slower. This results in a phase difference of 90 degrees between the two components.

**Hint:** Think about how the phase difference affects the resultant polarization state of the light.

### Step 4: Determine the Resulting Polarization
Due to the 90-degree phase difference introduced by the quarter wave plate, the emergent light becomes elliptically polarized. This means that the electric field vector of the light traces out an ellipse over time.

**Hint:** Recall that elliptical polarization is a general case that includes linear and circular polarization as special cases.

### Step 5: Conclusion
Based on the analysis, we conclude that when ordinary light is made incident on a quarter wave plate, the emergent light is elliptically polarized.

**Final Answer:** The emergent light is elliptically polarized.