Is Snell's law applicable when a ray of light is incident normal to the optical boundary?

Options

A. No
B. Yes
C. incomplete data
D. none of these

Explanation

To determine whether Snell's law is applicable when a ray of light is incident normal to the optical boundary, we can follow these steps:

### Step 1: Understand Snell's Law
Snell's law relates the angles of incidence and refraction to the refractive indices of the two media. It is mathematically expressed as:
\[ n_1 \sin(r_1) = n_2 \sin(r_2) \]
where:
- \( n_1 \) is the refractive index of the first medium,
- \( n_2 \) is the refractive index of the second medium,
- \( r_1 \) is the angle of incidence,
- \( r_2 \) is the angle of refraction.

### Step 2: Analyze the Situation
When a ray of light is incident normal (perpendicular) to the optical boundary, the angle of incidence \( r_1 \) is 0 degrees.

### Step 3: Substitute the Angle into Snell's Law
Substituting \( r_1 = 0 \) into Snell's law:
\[ n_1 \sin(0) = n_2 \sin(r_2) \]
Since \( \sin(0) = 0 \), we have:
\[ n_1 \cdot 0 = n_2 \sin(r_2) \]
This simplifies to:
\[ 0 = n_2 \sin(r_2) \]

### Step 4: Analyze the Result
For the equation \( 0 = n_2 \sin(r_2) \) to hold true, \( \sin(r_2) \) must also be 0. This means that \( r_2 \) must be 0 degrees, indicating that the ray continues in the same direction without any deviation.

### Step 5: Conclusion
Since the ray of light does not deviate when it is incident normal to the optical boundary, Snell's law does not apply in this case. Therefore, the answer to the question is **No**.

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