Refraction of Light — Page 1 Transcript Notes

Refraction of Light

• Refraction of light is defined as the change in direction of light on passing from one medium to another because of change in speed.
• This phenomenon occurs when light moves from a less dense medium into a more dense medium (e.g., air into glass or water) and speeds up or slows down accordingly, which causes a change in direction.

What causes refraction

• Light changes speed when crossing from one medium to another.
• The change in speed results in a bending or change of direction of the light ray.
• In the transcript’s example, light passes from air into glass or water, and the light slows down in the new medium.
• The slowing down in a denser medium is what leads to the change in direction.

Diagram Context (as described in the transcript)

• The ray diagram shows light passing from air into glass or water.
• Media indicated: air (medium) and water (medium) (glass is also referenced as a possible second medium).
• Key components labeled in the diagram:
  • Incident Ray
  • Normal (the line perpendicular to the boundary at the point of contact)
  • Angle of incidence
  • Angle of refraction
  • Refracted Ray
• The diagram visually represents the boundary between two media and the change in ray direction when crossing it.

Key Terms and Notation

• Incident Ray: The ray of light approaching the boundary between two media.
• Normal: The line perpendicular to the boundary at the point where the incident ray strikes.
• Angle of Incidence: The angle between the incident ray and the normal. Often denoted as $i$.
• Refracted Ray: The ray of light after it passes into the second medium.
• Angle of Refraction: The angle between the refracted ray and the normal. Often denoted as $r$.
• Media involved in the example: air as the initial medium; glass or water as the second medium.

Notation used in the transcript

• The transcript explicitly mentions the "Angle of incident" and the "Angle of refraction" and labels the incident angle with the variable $i$ in the diagram.
• The refracted angle is indicated as the angle of refraction; in standard notation this is $r$ (though the transcript does not explicitly spell out the $r$ symbol beyond labeling).

Media specifics in the example

• Air is the initial medium.
• Glass or water is the second medium (the light slows down in moving from air to glass or water).

Fundamental takeaway

• Refraction = change in direction of light caused by a change in speed when crossing from one medium to another.
• The amount and direction of bending depend on the relative speeds of light in the two media and are described in terms of the angle of incidence and the angle of refraction (i and r).

Quick recap

• Refraction occurs due to a change in speed as light enters a different medium.
• The incident ray, the normal, the angle of incidence (i), the refracted ray, and the angle of refraction (r) are the central elements of the described diagram.
• Example setup demonstrates light moving from air into glass or water, where the light slows down and changes direction.