A plane polarised light is passed through a polaroid, when the polaroid is given one full rotation about the direction of light, then

Options

A. The intensity of transmitted light gradually decreases to zero and remains zero
B. The intensity of transmitted light gradually increases to maximum and remains maximum
C. There is no change in intensity
D. The intensity of transmitted light is maximum and zero two tirties during rotation

Answer

To solve the problem, we need to analyze how the intensity of plane polarized light changes as it passes through a rotating Polaroid.

### Step-by-Step Solution:

1. **Understanding Plane Polarized Light**:
- Plane polarized light consists of waves that oscillate in a single plane. When this light encounters a Polaroid, it can be absorbed or transmitted depending on the orientation of the Polaroid relative to the light's polarization direction.

**Hint**: Remember that the direction of polarization of light is crucial in determining how much light is transmitted through a Polaroid.

2. **Initial Condition**:
- Assume the plane polarized light is initially aligned with the Polaroid (0 degrees). At this position, the intensity of light transmitted through the Polaroid is at its maximum.

**Hint**: Maximum intensity occurs when the light's polarization direction aligns with the Polaroid's axis.

3. **Rotation of the Polaroid**:
- As the Polaroid is rotated from 0 degrees to 90 degrees, the intensity of the transmitted light decreases. At 90 degrees, the light is perpendicular to the Polaroid's axis, resulting in zero intensity.

**Hint**: The intensity follows Malus's Law, which states that \( I = I_0 \cos^2(\theta) \), where \( \theta \) is the angle between the light's polarization direction and the Polaroid's axis.

4. **Continuing the Rotation**:
- Continuing to rotate the Polaroid from 90 degrees to 180 degrees, the intensity will start to increase again as the Polaroid approaches alignment with the light's polarization direction (180 degrees).

**Hint**: The pattern of intensity change is periodic; it decreases to zero at 90 degrees and increases back to maximum at 180 degrees.

5. **Completing the Full Rotation**:
- After one full rotation (360 degrees), the Polaroid returns to its original position (0 degrees), and the intensity of light is again at maximum.

**Hint**: The intensity of light will vary between maximum and zero as the Polaroid rotates through 360 degrees.

6. **Conclusion**:
- The intensity of light varies in a sinusoidal manner, reaching maximum intensity twice (at 0 degrees and 180 degrees) and minimum intensity (zero) twice (at 90 degrees and 270 degrees).

**Final Answer**: The correct option is D: "the intensity of light varies such that it is twice maximum and twice zero."