Mammoth Memory

Light passing through a glass brick

We know that when light passes from one medium to another at an oblique (ie, not perpendicular) angle, the ray of light will change direction. When the light passes into a glass or perspex block and out again the light ray will change direction twice.

A ray of light changes direction each time it travels into a different medium.

The light ray passing through the air towards the glass block will be parallel to the light coming out of the glass block.

The ray of light passing into and the ray of light passing out of the glass are parallel.

If the light enters along the normal line i.e. perpendicular (at 90°) to the block then no refraction (change of direction) occurs.

Light travelling along the normal line will not be refracted but will slow down in the denser medium.

The light will be slowed down as it travels through the denser medium but it will NOT change direction.

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