### 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. **Applying the Law of Reflection**: - According to the Law of Reflection: \[ \text{Angle of Incidence} = \text{Angle of Reflection} \] - In this case, the angle of incidence is given as 30 degrees. Therefore, by applying the law: \[ \text{Angle of Reflection} = 30 \text{ degrees} \] 3. **Visualizing the Situation**: - Imagine a flat mirror. If you draw a line perpendicular to the mirror at the point where the light hits (this is the normal line), you can visualize the incoming light ray making a 30-degree angle with this normal line. When the light reflects off the mirror, it will also make a 30-degree angle with the normal line on the opposite side. #### Why Other Options Are Incorrect: - **Option B: 45 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 angles must be equal. - **Option C: 60 degrees**: - Similar to option B, this option incorrectly states that the angle of reflection is greater than the angle of incidence. The Law of Reflection clearly states that they must be equal. - **Option D: 90 degrees**: - This option implies that the light reflects straight back, which is not the case here. A 90-degree angle of reflection would mean the light is reflecting off the surface at a right angle, which does not apply when the angle of incidence is only 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 Line**: The normal line is crucial for measuring angles correctly. Always visualize or draw it to avoid mistakes. - **Ignoring the Law of Reflection**: This fundamental principle is key to solving problems involving reflection. Always apply it when dealing with reflective surfaces. ### Revision Summary: - The angle of incidence equals the angle of reflection (Law of Reflection). - For an angle of incidence of 30 degrees, the angle of reflection is also 30 degrees. - Visualize the normal line to help understand the angles involved. - Always remember that the angles are measured from the normal, not the surface itself.