[b]Note that light going in at 90[degree] doesn't Refract[/b] [ul] [li]Rays of light from one substance to another are bent, or [b]Refracted[/b][/li] [li]Light is refracted towards the [b]normal[/b], [b]if the speed is reduced by the substance[/b], and away from the [b]normal[/b], [b]if the speed increases, through the substance[/b][/li] [li]Light speed is denoted by [i]c[/i], and is approximately 300,000,000 m/s (3[multiply]10[sup]8[/sup]), but is only around 200,000,000 m/s in glass[/li] [/ul] [img src='https://res.cloudinary.com/deylrqt2d/image/upload/v1487954390/refraction_korwkg.svg'] In the case above: [highlight] [b]i[degree][/b] is the incident ray and [b]r[degree][/b] is the refracted ray [/highlight] [h3]Real and Apparent Depth[/h3] The real depth can be more or less than the visible depth (so it may look nearer or further than it actually is, due to the refractive index of a substance). [code] Real Depth = (Refractive index) [multiply] (Apparent depth) [/code]