Medium of Light

The substances through which light can pass easily are called Medium of Light.

It is divided into two types:

1. Denser Medium
2. Rarer Medium

Denser and Rarer Medium

• The medium in which velocity of light decreases is called denser medium.

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• The medium in which velocity of light increases is called rarer medium.

Denser and Rarer Medium

• The medium of light having high optical density is called denser medium.

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• The medium of light having low optical density is called rarer medium.

Note: Optical density is a measure of how much a medium slows down light passing through it, determined by the material’s refractive index rather than its physical mass. Optical density relates entirely to light transmission, meaning a physically less dense substance can actually be optically denser.

Refraction of Light

• The phenomenon of bending of light as it travels from one medium to another medium is called refraction of light.

Glass Slab

(Denser Medium)

Air

(Rarer Medium)

Air

(Rarer Medium)

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Refraction of Light

• Incident ray:
• Refracted ray:
• Emergent ray:
• Angle of Incidence:
• Angle of refraction
• Normal:
• Lateral displacement (shift):

But wait!

Do you Know ?

• What is Optics?
• What is light?
• What is ray?
• What is beam?

• The branch of physics which deals with the study of light is called optics.
• Light is a form of energy which stimulates the sense of vision.
• A ray of light is a path along which the light travels.
• A collection of large no of rays is called beam.
• So, a ray is single and a beam is a bundle of rays.
• A beam of light can be parallel, convergent or divergent as shown below:

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Parallel Beam

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Convergent Beam

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Divergent Beam

Refraction of Light

• Incident ray: A light ray which strikes the surface that separates two mediums of light is known as incident ray.
• Refracted ray: The light ray obtained after refraction of light in second medium.
• Emergent ray: The ray of light which passes through one medium to another and again enters the same previous medium is emergent ray.
• Angle of Incidence: Angle made by incident ray with normal is called ….
• Angle of refraction: Angle made by refracted ray with normal is called ….
• Normal: It is the perpendicular drawn to the surface at the point of incidence.
• Lateral displacement (shift): The perpendicular distance between the direction of incident ray and emergent ray is called lateral shift.

Refraction of Light

Laws of Refraction of Light