05. Reflection

LEARNING TARGET

Solve problems involving the Law of Reflection

TASK:

Set up a mirror maze and sketch it in your notebook. Start with 3 mirrors and increase the number for complexity. You may use sand to visualize your LASER path. 

When waves hit the boundary between two different mediums (e.g. from air to glass) then there are two possible outcomes. Either the wave is transmitted across the boundary or it is reflected.

When light is reflected the law of reflection is always obeyed. The angle of incidence is equal to the angle of reflection.

Whenever we draw the type of diagram shown below we should always start by drawing in a normal line. This is a line (normally dashed) that is positioned perpendicular to the boundary and passing through the point where the light ray strikes the boundary. The angle of incidence is the angle between the incident ray and the normal, while the angle of reflection is between the reflected ray and the normal.

Different surfaces reflect light in different ways. A mirror is smooth even on a microscopic level. This means that the normal to the boundary is always pointing in the same direction and so all light gets reflected in the same direction. This type of reflection allows us to see an image (e.g. looking in a mirror or the surface of a still lake). Other objects reflect light so that we can see them but the boundary is not smooth so the normal lines are all in different directions. This means that as the light reflects it is scattered in all directions (the law of reflection is still obeyed though).

OR

When we look in a mirror we see the images of objects that appear to be within the mirror. These images are called virtual images, this means that light has never come from that image to our eyes. In fact our brain is tricked into thinking the light entering our eye has come from the virtual image. The light actually reflected at the boundary but our eyes don't know this and assume it has come in a straight line.