What is meant by the reflection of light? Reflection of light refers to the phenomenon where rays of light bounce back after striking a surface - Leaving Cert Physics - Question 7 - 2005

1. The incident ray, reflected ray, and normal at the point of incidence all lie in the same plane.
2. The angle of incidence is equal to the angle of reflection (i = r).

Apparatus: A ray box, drawing pins, and a plane mirror.

Procedure: Firstly, set up the ray box to shine a ray of light toward the plane mirror. Measure the angle of incidence (i) using a protractor. Place drawing pins along the path of the incident ray, mirror, and the reflected ray. Ensure that the incident ray, mirror, and reflected ray are in the same plane to validate the law of reflection.

Observation/Conclusion: You will observe that the angle of incidence is equal to the angle of reflection during the experiment, confirming the law of reflection.

Refraction is the bending of light as it passes from one medium to another. When light travels through different materials, such as from air into glass, it changes speed, leading to a change in direction.

The critical angle (θc) is the special name given to the angle of incidence when total internal reflection occurs.

To calculate the refractive index (n) of the glass, we can use Snell's law:

$n = \frac{\sin(i)}{\sin(r)}$

Assuming 'r' is the angle of refraction which is 67° in this case, we substitute:

$n = \frac{\sin(41.8°)}{\sin(67°)}$

This gives us a result of approximately n = 1.5.

Diagram:

       AIR
         |
         |
         B
         |
 -------|---------
        GLASS

One application of total internal reflection can be found in optical fibers. These are used in telecommunications to transmit data over long distances by bouncing light signals along the length of the fiber without loss of signal strength.