N1sinθ1 = n2sinθ2

Definition

The equation $$n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$$ is known as Snell's Law, which describes how light refracts, or bends, when it passes from one medium into another. This relationship highlights that the ratio of the sine of the angles of incidence and refraction is equal to the inverse ratio of the indices of refraction for the two media. It is essential for understanding various optical phenomena, including how lenses work and the principles behind total internal reflection.

5 Must Know Facts For Your Next Test

1. Snell's Law applies to all types of waves, but is most commonly associated with light waves in optics.
2. The index of refraction for air is approximately 1, while for water it is about 1.33 and for glass it can range from 1.5 to 1.9.
3. When light moves from a medium with a higher index of refraction to a lower one, it bends away from the normal line, resulting in a larger angle of refraction.
4. Total internal reflection occurs when light attempts to move from a denser medium to a less dense medium at an angle greater than the critical angle, leading to no refraction.
5. Applications of Snell's Law include designing optical devices like glasses, cameras, and fiber optic cables.

Review Questions

• How does Snell's Law apply when light transitions from air to water?
  • When light travels from air (with a lower index of refraction) into water (with a higher index), it slows down and bends towards the normal line. Using Snell's Law, $$n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$$ helps us calculate the angle of refraction. For instance, if the angle of incidence in air is 30 degrees, we can find the angle of refraction in water using their respective indices of refraction.
• What happens to the path of light when it moves from glass to air according to Snell's Law?
  • When light exits glass (higher index of refraction) into air (lower index), it bends away from the normal line. This behavior is predicted by Snell's Law, where we apply $$n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$$. The transition results in a larger angle of refraction compared to the angle of incidence, illustrating how light adapts its path based on the surrounding medium.
• Evaluate how total internal reflection demonstrates the principles outlined in Snell's Law.
  • Total internal reflection occurs when light moves from a denser medium to a less dense medium at an angle greater than the critical angle, leading to no transmission into the second medium. According to Snell's Law, this phenomenon illustrates that as the angle of incidence increases beyond this critical angle, $$n_1 \sin(\theta_c) = n_2 \sin(90^\circ)$$ simplifies to $$n_1 \sin(\theta_c) = 0$$ since sin(90°)=1. Thus, instead of refracting, all light reflects back into the denser medium, which is crucial for applications like fiber optics.

Related terms

Index of Refraction: A dimensionless number that describes how fast light travels through a medium compared to its speed in a vacuum.

Angle of Incidence: The angle between the incident ray and the normal line to the surface at the point of incidence.

Angle of Refraction: The angle between the refracted ray and the normal line after light has passed into a different medium.