Refraction is the bending of light as it passes from one medium to another with a different refractive index. This occurs due to the change in light's speed in different media.
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The Law of Refraction, also known as Snell's Law, is given by $n_1 \sin \theta_1 = n_2 \sin \theta_2$ where $n$ represents the refractive index and $\theta$ the angle.
The refractive index is a dimensionless number that describes how fast light travels through a material compared to vacuum.
When light moves from a medium with lower refractive index to higher refractive index, it bends towards the normal line.
Critical angle and total internal reflection occur when light moves from a medium with higher refractive index to one with lower refractive index.
Dispersion happens because different wavelengths of light are bent by different amounts when passing through materials.
Review Questions
What is Snell’s Law and how is it mathematically expressed?
Explain what happens to the direction of light when it passes from air (lower refractive index) into water (higher refractive index).
Define critical angle and describe its significance in refraction.
A dimensionless number that indicates how much the speed of light is reduced inside a medium; defined as $n = c/v$, where $c$ is the speed of light in a vacuum and $v$ is its speed in the material.
A phenomenon where all incident light is reflected back into a medium rather than being refracted, occurring when the incident angle exceeds the critical angle.