Light energy is a kind of kinetic energy that allows people’s eyes to see different light shades. The type of electromagnetic radiation produced by hot objects, such as lasers, lamps, and the sun, are characterized by light travelling in the form of a wave. Light energy is swift and moves faster, with a speed of 186,282 miles per second.

Light includes photons that are minute energy bundles. As the atoms of an object heat up, photons are emitted and produced. The electrons are excited by heat and accumulate extra energy, emitted as a photon, and the material becomes hotter with more photons.

Light has different types of essential properties, and these are as follows:

• Light rays move in a straight line
• The travelling speed of light is 3 x 10⁸ m/s, which is much faster than sound
• Diffraction of light
• Dispersion of light
• Reflection of light
• Refraction of light
• Polarization of light

Reflection of light occurs as the waves encounter a reflecting surface or its borders, not absorbing the radiation energy while the waves bounce back from the body. When light rays reflect a body, they travel from one transparent medium to another or move through a medium with a frequently altered composition. According to the law of reflection:

• The incident ray, the reflected ray and the normal to the surface at the point of incidence all lie in the same plane.
• The angle of incidence is equal to the angle of reflection.

The definition of refraction states that it is a process where the speed of light changes as it passes from a medium to another medium, resulting in light beams’ bending. Refraction of light obeys two of the following laws:

• The incident ray, the reflected ray and the normal to the surface at the point of incidence all lie in the same plane.
• The ratio of the sin of the angle of incidence to the sin of the angle of refraction is always constant for a given pair of media and the light of the given wavelength.

One of the simplest examples of refraction is a half-filled glass of water with a pencil. See how the crayon looks normal above the water, but it seems much more significant and curved under the water. It happens as a result of refraction.

A mirror is a reflective plate that springs from light and produces an image or a virtual image. When an object is set before a mirror, it is visible as its reflection in the mirror. The item is the ray source, and the representation consists of the reflected rays. The images are known as real images or composite images based on the relationship between light. A real image is produced when the light rays converge, while virtual pictures arise due to the light rays’ apparent divergence.

Mirrors are of two types, namely a plane mirror and a spherical mirror. A plain reflecting mirror has a flat and smooth reflection, while a spherical mirror or curved mirror is a mirror with a constant curve and a constant curvature radius.

Curved mirrors are mirrors with curved surfaces on one edge. There are two types of curved mirrors, namely convex and concave mirrors. Spherical mirrors with interior surfaces are known as convex mirrors, while spherical mirrors with exterior surfaces are known as concave mirrors.

1. Convex mirror
   The curved mirror that bulges outward towards the light source is known as a convex mirror or divergent mirror. Convex mirrors reflect light externally, such that these are not used for focusing. These mirror images cannot be projected onto the screen because the image is smaller than the object but grows as the object gets close to the mirror.
   
   
2. Concave mirror
   A concave mirror has a reflective layer recessed within a mirror (away from the incident light). The concave mirror reflects light in a single focus as these are used to focus light. Concave mirrors display varying images according to the distance from the source to the mirror compared to convex mirrors.

There are numerous uses of curved mirrors and are listed as follows:

• Curved surfaces of concave mirrors are used most often in shaving.
• The ophthalmoscope is composed of a concave mirror and a central hole. The doctor focuses from behind the concave mirror into the narrow spot, and a ray of light is directed to the patient’s pupil.
• Concave mirrors are often used as reflectors in automotive and motor vehicle lamps, flashlights, train engines.
• A concentric mirror of 5 metres or more is used as the target in an astronomical telescope.
• Convex mirrors are used extensively in cars as rear-view mirrors.
• Convex mirrors are commonly used in the production of magnifying lenses. Two convex mirrors are positioned back-to-back to create a magnifying lens.
• Massive companies, shops and hospitals use a convex mirror to allow pedestrians to see the corner to deter collisions.
• Convex mirrors in different locations are often used for safety purposes. It is located in an ATM vicinity, so bank clients can see if someone is behind them.

A variety of technological advances have turned around light over the last century. Optical research has allowed us to develop our knowledge of light energy and its relationships with all sorts of matter.

1. Why is light considered a source of energy?
   According to Einstein, light has no energy because it has no mass, but how can sunlight heat the planet without energy? In reality, despite no mass, light carries energy through its momentum.
   
2. What are the different types of light?
   They are visible rays, infrared rays, X-rays, and UV rays.
3. Which colour of light has the highest and lowest energy?
   Violet is having the highest while red is having the least amount of energy.
4. Which phenomenon is responsible for the blue colour of the sky?
   Rayleigh scattering.