Refraction is the bending of light due to the change in the speed of light
when passing through 2 transparent materials having different optical
densities.
Key Terms Used in Refraction of Light
Incident ray is the ray of light before it crosses the boundary between 2
transparent materials.
Refracted ray is the bent ray as the light passes after the boundary between 2
transparent materials.
Normal is an imaginary line perpendicular to the interface of media where the
refraction occurs.
Angle of incidence (Li) is the angle between incident ray and the normal.
Angle of refraction (Lr) is the angle between refracted ray and the normal.
Laws of Refraction
First Law of Refraction states that the incident ray, the refracted ray and the
normal to the interface all lie in the same plane.
Second Law of Refraction states that for two given media, the ratio constant
sin i /sin r = constant, where i is the angle of incidence and r is the angle of
refraction. Refractive Index
The refractive index / index of refraction is a measure of how much the speed
of light is reduced inside a medium compared to the speed of light in a
vacuum.
The refractive index (n) of a material is defined as the ratio of the speed of Magnifying lens produces an upright,
light in a vacuum (c) to the speed of light in the material (v). It is given by the enlarged and virtual image that
formula: makes the object located between
n=c/v the F and the vertex of a convex lens.
The refractive index is also given by the formula:
n = sin i / sin r
Projector produces an enlarged and
Material Refractive Index real image that makes the object
Air 1.003 located Between F and 2F using a
Water 1.333 convex lens.
Acetone 1.360
Dense flint glass 1.655
Diamond 2.417
The camera and the lens of the eye
Key Points of Refractive Index produce a real, inverted and reduced
image that makes the object located
• The refractive index of a medium is always greater than 1, since light
beyond 2F using a convex lens.
travels slower in any medium than it does in a vacuum. For example,
the refractive index of air is approximately 1.0003, and for typical
glass, it’s around 1.5. This means light travels about 1.5 times slower Photo
in glass than in a vacuum.
• The greater the value of the refractive index of a medium, the
greater is the “bending” effect (refraction) of light when it passes
from air into that medium.
• A material with a larger value of n is an optically denser medium.
• The higher the refractive index of a medium, the slower the speed of
light will be through it. This means that a medium’s optical density
increases as its refractive index increases.
Applications:
Photocopier produces the same
size as the object making the
object located At 2F of a convex
lens.
