Railway Science (Physics-Light and Optics) (Part-V)

Virtual and diminished image will be formed at Between P and F, behind the mirror.

Regular. Reflection of light may be classified as regular reflection and diffused reflection. When the reflecting surface is very smooth and the rays of light falling on it are reflected straight off it, then it is called regular reflection. When the reflection of light takes place from a rough surface the light is reflected off in all directions, called diffused reflection.

Iris is the colored part of the eye that surrounds the pupil. It adjusts the size of the pupil to control the amount of light that enters the eye. The pupil is the opening at the center of the iris through which light passes.

Same shape, straight, laterally inverted, virtual. A plane mirror is a flat mirror that reflects light and produces a virtual image without the interference of an inward or outward curve. Image formation by plane mirror: The size of the image is equal to that of the object. The image formed is as far behind the mirror as the object is in front of it. Uses - Solar cookers, and Periscope.

Half of its radius of curvature (f=R/2). Focal Length of a Spherical Mirror: The distance between the mirror and the point where incident light rays parallel to the axis converge. It influences the behavior of a mirror, affecting the type of image it forms and the size of that image.

Luminous objects. For example, the Sun, stars, electric bulbs, torches, tube lights. Transparent objects: These objects allow light to pass through them completely. Examples - glass and water. Translucent objects: These objects allow some light to pass through them. Examples- frosted glass and wax paper.

2.42. The ratio of the speed of light in air or vacuum to the speed of light in the medium is called the refractive index of that medium. It is generally denoted by ‘μ’ or ‘n’. It is a dimensionless quantity. The absolute refractive index can never be less than 1.

Virtual and lateral inverted. Image formed by a plane mirror is always virtual and erect. The size of the image is equal to that of the object. The image formed is as far behind the mirror as the object is in front of it. Further, the image is laterally inverted.

Ciliary body: A circular structure that is an extension of the iris (the colored part of the eye) Ciliary body produces the fluid in the eye called aqueous humour. It also contains the ciliary muscle, which changes the shape of the lens when the eyes focus on a near object.

Focus. Aperture - A point in a mirror or lens from which light rays actually come. Principal Axis - The central line in an optical system, along which light travels, connecting the center of the lens/mirror to the focal point. Pole - The geometrical center of the spherical surface of the mirror or lens.