9: Reflection and Refraction

Use a ray box, a lens and a slit.

Ray boxes get hot, switch off when not in use.

We can do this practical using a laser, but it is more dangerous.

• Take A3 paper and draw a line down the centre (ruler)

• Draw a line at right angles (protractor). This is the normal, we label this N.

• Now place a glass block against the first line, so the normal is at the centre of the block.

• Now we draw around the glass block.

• Turn off all of the lights in the room. Use the ray box to direct a ray of light so it hits the block at the normal. This is the incident ray. The angle between the incident ray and normal is the angle of incidence.

• Adjust the ray box to change the angle of incidence. At a certain angle, we can see a ray reflect from the surface of the block. We can also see another ray leaving the block from the opposite side. This is the transmitted ray.

• Mark the path of the incident ray, the reflected ray and the transmitted ray using crosses.

• Turn on the room lights and switch off the ray box. Remove the glass box.

• Draw in the incident ray and reflected ray. Draw in the transmitted ray so it meets the position of the block. Draw a line to show the path of the transmitted ray through the glass block.

• Measure the important angles.

• Angle of reflection is the angle between the normal and the path of transmitted ray through the block.

• Angles of incidence and reflection do not depend on material.

• Angle of refraction is different for different materials.