Optics

Last Updated : 22 May, 2024

Optics is an important branch of physics, that tells about the behavior of light when interacting with various mediums and surfaces, phenomena like the formation of the rainbow, working of the microscope, answering questions about how light travels, reflects, refracts and forms images, etc. It is important for the development of various revolutionized fields including communication and healthcare, astronomy, and entertainment.

In this article, we will study optics, concepts, and formulas related to optics.

What is Optics?

Optics is the branch of physics that deals with the study of light and its interactions with matter. It encompasses the behavior of light, the properties of optical instruments, and the phenomena associated with the transmission, reflection, refraction, diffraction, and polarization of light.

Optics plays a crucial role in understanding how light behaves and is manipulated in various applications, including imaging, communication, microscopy, spectroscopy, and laser technology.

Important Terms Related to Optics

The important terms related to optics are:

Lights

Light is a form of electromagnetic radiation that is visible to the human eye. It is composed of tiny packets of energy called photons, which travel in waves. Light plays a fundamental role in our perception of the world, allowing us to see objects, colors, and shapes.

Beyond its role in vision, light has profound effects on various natural phenomena and is essential for sustaining life on Earth through processes such as photosynthesis.

Relationship Between Wavelength and Energy

The relationship between Wavelength and Energy is given by:

E=hc/λ

here ,

E is the energy of the radiation
h is Planck's constant,
λ is the wavelength of the radiation.

Reflection of Light

Phenomenon of bouncing back of light in the same medium after striking a shining surface like mirror is called Reflection.

Laws of Reflection

There are two laws of reflections:

First Law: The incident ray, the reflected ray, and the normal (a line perpendicular to the surface at the point of incidence) all lie in the same plane.
Second Law: The angle of incidence (i) is equal to the angle of reflection (r), measured from the normal.

Mirror

A mirror is an object with a reflective surface that reflects light rays, allowing the formation of images of objects placed in front of it. Mirrors are commonly used for various purposes, including personal grooming, decoration, and optical instruments.

Types of Mirror

Mirrors are further classified into three types which are described below:

Plain Mirror

A plain mirror, also known as a flat mirror, has a smooth and flat reflective surface. It reflects light rays according to the laws of reflection.

Image is formed behind the mirror at the same distance as the object, with the same size and orientation and is virtual.

Concave Mirror

A concave mirror is curved inward, resembling a section of the inner surface of a sphere. It reflects light rays in a manner that converges them towards a focal point.

Convex Mirror

A convex mirror is curved outward, resembling a section of the outer surface of a sphere. It reflects light rays in a manner that diverges them away from a focal point.

Also Check, Mirror Formula and Magnification

Images

There are mainly two types of images that are formed due to reflection:

Real Image

Real images are formed by the actual convergence of light rays after passing through an optical system. They can be projected onto a screen and captured on a surface. It is formed on the opposite side of the optical system as the object.

Virtual Images

Virtual images are formed by the apparent convergence of light rays after passing through an optical system. It cannot be projected onto a screen and do not exist in physical space. It formed on the same side of the optical system as the object.

Refraction of Light

Phenomenon of bending of light rays after passing from denser medium to rarer medium toward the normal and away from the normal when passing from rarer to denser medium is called refraction of light. It is because of change of speed of light , because different mediums have different refractive index ,which indicates how much light slows down when passing through it compared to its speed in a vacuum.

Snell's Law

Snell's law, also known as the law of refraction, states that the ratio of the sine of the angle of incidence (θ₁) to the sine of the angle of refraction (θ₂) is equal to the ratio of the velocities of light in the two respective mediums. Mathematically, it can be expressed as:

n₁ x sinθ₁= n₂ x sinθ₂

Where:

?₁and ?₂ are the refractive indices of the first and second mediums, respectively.
?₁ is the angle of incidence (the angle between the incident ray and the normal to the interface between the two mediums).
?₂ is the angle of refraction (the angle between the refracted ray and the normal to the interface).

Lenses

A lens is a transparent optical device that refracts (bends) light rays as they pass through it. Lenses are typically made of glass or plastic and have curved surfaces that can converge or diverge light rays, depending on their shape and curvature.

Types of Lenses

Lenses can be classified into two main types based on their shape and refractive properties:

Concave Lens

A concave lens is thinner at the center and thicker at the edges, resembling a recessed or curved inward shape. It causes light rays to diverge or spread apart after passing through it.

Convex Lens

A convex lens is thicker at the center and thinner at the edges, resembling a bulging outward shape. It causes light rays to converge or come together after passing through it.