### Correct Option: A. 30 degrees ### Detailed Explanation: When light strikes a surface, such as a flat mirror, it follows a fundamental principle known as the law of reflection. This law states that the angle of incidence is equal to the angle of reflection. 1. **Understanding the Terms**: - **Angle of Incidence (i)**: This is the angle formed between the incoming ray of light and the normal (an imaginary line perpendicular to the surface at the point of incidence). - **Angle of Reflection (r)**: This is the angle formed between the reflected ray of light and the normal. 2. **Applying the Law of Reflection**: - According to the law of reflection: \[ \text{Angle of Incidence} (i) = \text{Angle of Reflection} (r) \] - In this case, the angle of incidence is given as 30 degrees. Therefore, we can write: \[ i = 30^\circ \] - By the law of reflection, we can conclude: \[ r = 30^\circ \] 3. **Conclusion**: - Since the angle of incidence is 30 degrees, the angle of reflection is also 30 degrees. Thus, the correct answer is **A. 30 degrees**. ### Explanation of Other Options: - **Option B: 60 degrees**: - This option suggests that the angle of reflection is 60 degrees. However, this would imply that the angle of incidence was 60 degrees, which contradicts the given information that the angle of incidence is 30 degrees. Therefore, this option is incorrect. - **Option C: 90 degrees**: - This option indicates that the angle of reflection is 90 degrees. For this to be true, the angle of incidence would have to be 90 degrees as well. Since the angle of incidence is 30 degrees, this option is also incorrect. - **Option D: 15 degrees**: - This option suggests that the angle of reflection is 15 degrees. Similar to the previous options, this would imply a different angle of incidence, which is not the case here. Therefore, this option is incorrect. ### Common Pitfalls: - **Confusing Angle of Incidence with Angle of Reflection**: It's crucial to remember that these two angles are equal according to the law of reflection. - **Misunderstanding the Normal Line**: The normal line is always perpendicular to the surface at the point of incidence. Ensure you visualize this correctly when determining angles. - **Forgetting to Measure Angles from the Normal**: Always measure angles from the normal line, not from the surface of the mirror. ### Revision Summary: - The angle of incidence equals the angle of reflection (Law of Reflection). - For a ray striking a flat mirror at 30 degrees to the normal, the angle of reflection is also 30 degrees. - Always visualize the normal line when working with angles of incidence and reflection. - Double-check your understanding of the definitions of incidence and reflection to avoid common mistakes.