Physics — Light & Optics

A convex mirror always forms a virtual, erect, and diminished image regardless of the object's position.

According to Cauchy's equation, the refractive index is highest for violet (shortest wavelength) and lowest for red (longest wavelength), causing red light to deviate the least.

Myopia (nearsightedness) occurs when light focuses in front of the retina; it is corrected using a concave lens to diverge light before it enters the eye.

The speed of light in a vacuum is a universal physical constant denoted as 'c', approximately 299,792,458 meters per second.

When light travels between media, its speed and wavelength change, but its frequency remains constant because it depends on the source of light.

Twinkling is caused by atmospheric refraction, where the varying density of air layers continuously bends starlight as it reaches the observer.

Rayleigh scattering causes shorter wavelengths of light (blue and violet) to scatter more strongly than longer wavelengths in the atmosphere.

Endoscopes use optical fibers that transmit light through multiple total internal reflections, allowing for imaging inside the body.

A negative sign for magnification indicates a real and inverted image, while the magnitude 2 indicates the image is magnified.

Convex mirrors are used because they provide a wider field of view and always produce erect, diminished images.

The power of a lens (P) is the reciprocal of its focal length in meters, measured in Dioptre (D).

Diffraction is the bending of light waves around the edges of an obstacle or through an aperture.

The critical angle is the angle of incidence in a denser medium for which the angle of refraction in the rarer medium is 90°.

In the visible spectrum, red light has the longest wavelength (approx. 700 nm), while violet has the shortest.

A real image is one that can be projected onto a screen, created by the actual convergence of light rays.

A photometer is a device that measures the luminous intensity of light or the intensity of a light source.

Total internal reflection only occurs when light travels from a medium of higher refractive index (denser) to one of lower refractive index (rarer).

A virtual image is formed when light rays appear to diverge from a point; it cannot be projected onto a physical screen.

The refractive index is a function of the wavelength of light; this dependence is known as dispersion.

Optical fibers work on the principle of Total Internal Reflection (TIR), where light is trapped and guided through the core without significant loss.

Light slows down when entering a denser medium and bends towards the normal line to obey Snell's Law.

Persistence of vision is the characteristic of the human eye that causes an image to remain on the retina for a fraction of a second (approx 0.0625s) after the stimulus is removed.

A concave mirror is called a converging mirror because it reflects parallel rays of light to a single focal point.

The refractive index of water is higher than air, reducing the relative refractive index of the lens material, which increases the focal length.

Mirages occur due to the variation in the refractive index of air layers near the hot ground, causing total internal reflection of light from the sky.

The cornea is the outermost transparent layer and is responsible for the majority of the eye's refractive power.

Dispersion is the phenomenon of splitting white light into its constituent seven colors (VIBGYOR) upon passing through a prism.

When an object is placed at C in a concave mirror, the image is real, inverted, and of the same size, formed exactly at C.

Atmospheric refraction causes light rays from the sun to bend as they pass through layers of varying density, allowing us to see the sun before it crosses the horizon.

Concave mirrors are used by dentists because they produce a magnified and erect image when the object is held close to the mirror.

A ray of light passing through the optical center of a lens continues its path without any deviation.

A concave (diverging) lens is thinner at the middle and thicker at the edges, causing parallel rays to spread out.

According to Rayleigh's law, intensity of scattered light is inversely proportional to the fourth power of its wavelength; thus, violet/blue scatters the most.

The refractive index is defined as the ratio of speed of light in vacuum to the speed of light in the medium; for vacuum, it is 1.

The eye lens acts as a convex lens, creating a real and inverted image on the retina, which the brain interprets as erect.

Mirror surfaces are coated with a reflective material (like silver or aluminum) to enhance the regular reflection of light.

Power (P) = 1/f (in meters). P = 2, so f = 1/2 = 0.5 meters, which is 50 cm.

Diffraction is the slight bending of light as it passes around the edge of an object or through a narrow slit.

A plane mirror can be considered as a sphere with an infinite radius of curvature; since R = 2f, the focal length is also infinite.

According to Snell's Law, when light moves from a denser medium (like glass) to a rarer medium (like air), its speed increases, causing it to bend away from the normal.

When a point source of light is placed at the focus of a concave mirror, the reflected rays emerge as a parallel beam.

The bending of light as it moves from water to air due to the change in optical density causes the object to appear at a different position, a phenomenon known as refraction.

Power P = 1/f (in meters). P = -2.5D, so f = 1/-2.5 = -0.4m = -40 cm. A negative focal length indicates a concave lens.

The Tyndall effect is the scattering of light by particles in a colloid or a very fine suspension, such as light paths visible through dust or fog.

The iris acts as a diaphragm that expands or contracts the pupil to regulate the intensity of light entering the eye.

In the visible spectrum, Violet has the shortest wavelength and highest frequency, while Red has the longest wavelength.

When an object is at the focal point (F), the refracted rays become parallel and are considered to meet at infinity.

A convex mirror (diverging mirror) always produces a virtual, erect, and smaller-than-object image, which is why it is used as a rear-view mirror.

Refractive index (n) = c/v. A value of 2.42 means light travels 2.42 times slower in diamond than in a vacuum.