### Correct Option: A. 30 degrees ### Detailed Explanation: When light strikes a reflective surface, 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 Angles**: - The angle of incidence is the angle formed between the incoming light ray and the normal (an imaginary line perpendicular to the surface at the point of incidence). - The angle of reflection is the angle formed between the reflected light ray and the normal. 2. **Given Information**: - In this problem, the angle of incidence is given as 30 degrees. 3. **Applying the Law of Reflection**: - According to the Law of Reflection: \[ \text{Angle of Incidence} = \text{Angle of Reflection} \] - Therefore, if the angle of incidence is 30 degrees, the angle of reflection must also be 30 degrees. 4. **Conclusion**: - Thus, the angle of reflection when the beam of light strikes the reflective surface at an angle of 30 degrees to the normal is also 30 degrees. ### Why Other Options Are Incorrect: - **Option B: 60 degrees**: - This option suggests that the angle of reflection is greater than the angle of incidence. According to the Law of Reflection, this is incorrect because the angle of reflection must equal the angle of incidence. - **Option C: 90 degrees**: - This option implies that the light is reflecting straight out from the surface, which is not the case here. The angle of incidence is only 30 degrees, so the angle of reflection cannot be 90 degrees. - **Option D: 45 degrees**: - This option also does not follow the Law of Reflection. The angle of reflection cannot be 45 degrees if the angle of incidence is 30 degrees. ### Common Pitfalls: - **Confusing Angles**: Students often confuse the angle of incidence with the angle of reflection. Remember, they are always equal. - **Misunderstanding the Normal**: The normal line is crucial in determining angles. It is always perpendicular to the surface at the point of incidence. - **Ignoring the Law of Reflection**: Always apply the Law of Reflection when dealing with reflective surfaces. ### Revision Summary: - The angle of incidence equals the angle of reflection (Law of Reflection). - If the angle of incidence is 30 degrees, the angle of reflection is also 30 degrees. - The normal line is essential for measuring angles in reflection problems. - Always double-check your understanding of the definitions of incidence and reflection angles.