Reflection and refraction of light, laws and principles

Reflection is the phenomenon where light bounces back from a surface.
The law of reflection states that the angle of incidence (i) is equal to the angle of reflection (r).
Reflection occurs at the boundary of two mediums, such as air and a mirror.
Reflection can be regular (on smooth surfaces) or diffuse (on rough surfaces).
Plane mirrors produce virtual, upright, and laterally inverted images.
Spherical mirrors are classified as concave and convex mirrors.
Concave mirrors focus light and can form real or virtual images depending on the object’s position.
Convex mirrors diverge light and always form virtual, upright, and diminished images.
The focal length of a mirror is half the radius of curvature (f = R/2).
The mirror formula is given by 1/f = 1/v + 1/u, where f is the focal length, v is the image distance, and u is the object distance.

Refraction is the bending of light as it passes from one medium to another with different densities.
The refractive index (n) is the ratio of the speed of light in a vacuum to its speed in a medium (n = c/v).
The law of refraction, or Snell’s Law, states that n₁sinθ₁ = n₂sinθ₂, where n₁ and n₂ are the refractive indices.
Refraction causes phenomena like the apparent bending of a pencil in water.
The critical angle is the angle of incidence for which the angle of refraction is 90°.
Total internal reflection occurs when light travels from a denser to a rarer medium at an angle greater than the critical angle.
Lenses work on the principle of refraction, forming images based on their shape and material.
Converging lenses (convex) focus light to a point, while diverging lenses (concave) spread light.
The lens formula is 1/f = 1/v - 1/u, similar to the mirror formula.
Prisms refract light and can disperse it into its constituent colors, creating a spectrum.

Light exhibits both wave and particle nature (wave-particle duality).
The speed of light in a vacuum is approximately 3 × 10⁸ m/s.
Light travels slower in denser mediums, which increases its refractive index.
Visible light has wavelengths ranging from 400 nm (violet) to 700 nm (red).
Reflection and refraction are essential for designing optical instruments like telescopes and microscopes.

Mirrors are used in daily life, such as in rearview mirrors and makeup mirrors.
Lenses are used in spectacles, cameras, and projectors to focus light.
Total internal reflection is used in fiber optics for high-speed data transmission.
Prisms are used in optical devices like periscopes and spectrometers.
Understanding reflection and refraction is vital for studying phenomena like rainbows and mirages.
Reflecting telescopes and refracting telescopes rely on these principles to observe celestial bodies.

Refraction explains the twinkling of stars and the apparent shift of objects under water.
Reflection causes image formation in mirrors.
Rainbows are formed due to the dispersion of light in water droplets, involving both reflection and refraction.
Mirages occur due to the refraction of light in layers of air with different temperatures.
The sky appears blue because of the scattering of shorter wavelengths of light.