Refraction of Light (Laws of Refraction, Lenses) - SS2 Physics Lesson Note

Refraction of light is the bending of light waves as they pass from one medium to another with a different optical density. It is a fundamental phenomenon that occurs when light transitions between mediums such as air, water, glass, or any other transparent material. Refraction plays a crucial role in various optical systems and devices, including lenses, prisms, and optical fibres.

The laws of refraction, also known as Snell's laws, govern the behaviour of light during refraction:

1.    The incident ray, the refracted ray, and the normal to the interface between the two mediums all lie in the same plane.

2.    The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media. This ratio is known as the refractive index of the second medium with respect to the first medium.

Mathematically, Snell's law can be expressed as:

n₁sinθ₁ = n₂sinθ₂

where n₁ and n₂ are the refractive indices of the first and second mediums, respectively, and θ₁ and θ₂ are the angles of incidence and refraction.

Refraction can be observed when light passes through a lens, which is a transparent optical component with a curved surface(s). Lenses are commonly used in optical systems to focus, diverge, or manipulate light. There are two types of lenses:

Convex Lenses:

Convex lenses are thicker at the centre and thinner at the edges. They converge parallel light rays and focus them to a point called the focal point. Convex lenses are also known as converging lenses. Depending on the position of the object relative to the lens, convex lenses can form either real or virtual images. Real images are formed when the object is placed beyond the focal point, and virtual images are formed when the object is placed between the lens and the focal point.

Concave Lenses:

Concave lenses are thinner at the centre and thicker at the edges. They cause parallel light rays to diverge. Concave lenses are also known as diverging lenses. When light passes through a concave lens, it appears to originate from a point called the virtual focal point. Images formed by concave lenses are always virtual, smaller in size, and located on the same side of the lens as the object.

The study and understanding of refraction are essential in various applications. Lenses are widely used in optics, vision correction, photography, and imaging systems. They are key components in devices such as cameras, telescopes, microscopes, and eyeglasses. The principles of refraction are also utilised in other optical components like prisms and fibre optics, enabling the transmission and manipulation of light signals in communication systems.

In summary, refraction of light occurs when light waves pass from one medium to another with a different optical density. The laws of refraction govern this phenomenon, ensuring the conservation of energy and momentum. Lenses, including convex and concave lenses, utilise refraction to focus or diverge light, forming real or virtual images. The study of refraction and the use of lenses have significant implications in various fields, contributing to advancements in optics, imaging, and communication technologies.