I carried out an experiment to show that the angle of reflection of light is the same as the angle of incidence.
Aim: To investigate the theory of reflection that the angle of reflection is the same as the angle if incidence.
- Light box
- Camera to show experiment
- A4 paper to record results
- Independent Variable – Angle of incidence.
- Dependent Variable –Angle of reflection.
- Controlled Variable –protractor, light box, mirror, position of mirror
- Connect the light box to the transformer.
- Then plug the transformer to a socket.
- Turn on the transformer to full power then turn on the light box.
- Use a single slot filter for the light box.
- Place the light box at a 90° angle to the mirror which is tilted 45° on top of the A4 paper.
- Trace the light’s path along the paper form the light box to the reflection and the reflective side of the mirror.
- Measure the normal. From the normal, measure the angle from the normal to the incidence ray. Then measure the reflective angle, from the normal. They should be equal according to the Law of Reflection
Diagram of the Reflection of Light
Angle of Incidence: 45°
Angle of Reflection: 45°
This experiment proves that light is not a wave because it shows that the angle of incidence and the angle of reflection are equal.
Reliability and Validity:
This experiment has very few variables. This is also supported by the fact that modern equipment are consistently made accurately
such as mirrors and light boxes hence you would get the same result every time you try this experiment. During my time, I ground my own mirrors and they were not as accurate as they are now because each one is slightly different. However, by keeping all of the apparatus the same in each of the experiments, I was able to remove variables such as difference in reflectivity of mirrors to make this experiment more reliable and valid. All of these aspects make this a successful experiment which can be produced many times with the same outcome have made this a valid experiment.
Isaac Newton’s View:
The particle theory justifies why reflection happens. Some scientists, such as Aristotle and Christiaan Huygens, believe that light travels in waves. I however, believe that light is made up of particles (corpuscles), which travel in straight lines which this experiment proves. How can a wave travel in a straight line when you can hear sound from around a corner? In this experiment we see the reflection of the corpuscles in straight lines, at the same angle as they were projected. These angles, the angle of incidence and the angle of reflection, are equal which proves that light is not a wave.
View of a Modern Scientist:
Modern scientists, defines reflection as the change in direction of a wave front at an interface between two different media so that the wavefront returns into the medium from which it originated. Light travels in a straight line through a substance of uniform density. For example, you can see the straight path of light rays admitted through a narrow slit into a darkened room. The straight path of the beam is made visible by illuminated dust particles suspended in the air. If the light is made to fall onto the surface of a mirror or other reflecting surface, however, the direction of the beam changes sharply.