Class 9 Physics - Laws of Reflection

Aim

To study the laws of reflection of light, which state that the angle of incidence is equal to the angle of reflection, and the incident ray, the reflected ray, and the normal to the surface at the point of reflection all lie in the same plane.

Materials Required

• Flat mirror
• Light source (like a ray box or laser pointer)
• Protractor
• Drawing paper
• Ruler or scale
• Pencil for marking rays

Image Reference

Procedure

1. Place the flat mirror on a sheet of drawing paper and trace the outline of the mirror to mark its position.
2. Position the light source at a specific angle relative to the mirror, ensuring that the light ray strikes the mirror surface.
3. Draw the incident ray from the light source to the mirror and the reflected ray after it strikes the mirror surface.
4. Use a protractor to measure the angle of incidence (the angle between the incident ray and the normal to the surface at the point of reflection).
5. Measure the angle of reflection (the angle between the reflected ray and the normal to the surface at the point of reflection).
6. Ensure that the angles of incidence and reflection are equal as per the law of reflection.
7. Repeat the experiment by varying the angle of incidence and verify the law of reflection each time.

Observation

The angle of incidence is found to be equal to the angle of reflection. This confirms the first law of reflection, which states that the angle of incidence is equal to the angle of reflection.

Furthermore, the incident ray, the reflected ray, and the normal to the surface all lie in the same plane, which is the second law of reflection.

Precautions

• Ensure the mirror is clean and free from any dust or obstructions to obtain accurate results.
• Make sure the light source is stable and directed at the mirror at a fixed angle for each trial.
• Use a protractor with precision to accurately measure the angles of incidence and reflection.
• Ensure the mirror is placed flat on the paper to maintain correct alignment of the rays.

Conclusion

The law of reflection is verified, where the angle of incidence is equal to the angle of reflection, and both rays lie in the same plane as the normal at the point of reflection.

Video Reference