Light, Vision and Electricity

When red light falls on objects, the color we see depends on what light each object absorbs or reflects. A green leaf appears green because it absorbs red light and reflects green. Therefore, under red light, the green leaf absorbs all the red and appears black. A red flower reflects red light, so it continues to appear red under red light.

Blue light is scattered most by air molecules due to Rayleigh scattering (scattering intensity ~1/λ^4). Reflection would bounce light back unchanged, while interference and diffraction don't cause the sky's blue color.

A red rose appears red because it reflects red light and absorbs other colors including green. Under pure green light, no red light is available to reflect, so the rose absorbs all incident light and appears black (no reflection).

Yellow light has a longer wavelength that scatters less in fog compared to white light (Rayleigh scattering decreases with longer wavelength). This gives better penetration through fog particles, improving visibility. Yellow light also causes less eye strain than white light.

Violet light has the shortest wavelength and highest frequency in the visible spectrum, causing it to deviate (refract) the most when passing through a prism due to dispersion. Red light refracts the least, creating the familiar rainbow spectrum with red on the outer edge.

25 cm is the standard near point (closest distance for comfortable focusing) for a normal human eye. At distances closer than this, the eye's ciliary muscles must contract maximally to accommodate, causing strain. This is an average value - near point can vary with age and individual differences.

When an object is placed between two parallel mirrors, light bounces back and forth infinitely. Each reflection becomes a new object for the next reflection, creating theoretically infinite images. In practice, images become progressively dimmer due to absorption at each reflection.

In a plane mirror, the image distance equals the object distance from the mirror surface. When you move 1 m/s toward the mirror, your image also moves 1 m/s toward you from the opposite side. The relative speed between you and your approaching image is therefore 1 m/s (not 2 m/s).

For an astronomical telescope in normal adjustment, magnifying power M = fo/fe where fo is the objective focal length and fe is the eyepiece focal length. Increasing the objective focal length increases magnification proportionally, assuming the eyepiece focal length remains constant.

In a camera, focusing adjusts the lens-to-sensor distance to satisfy the lens equation 1/f = 1/u + 1/v. The lens must be positioned so that the image forms precisely on the sensor/film. Moving the lens changes the image distance to achieve sharp focus at different object distances.

A concave mirror produces an enlarged, upright virtual image of an object when placed close to it, which makes it ideal for use as a shaving or makeup mirror. Convex mirrors produce diminished images, while plane mirrors produce same-sized images.

Accommodation is the eye's ability to change the lens curvature via ciliary muscles to focus on objects at different distances. When viewing near objects, ciliary muscles contract to increase lens curvature; for distant objects, they relax to flatten the lens.

Convex mirrors diverge light rays, which allows them to cover a wider field of view in a compact reflection. This property makes them ideal for rear-view mirrors and security mirrors where seeing a broad area is more important than magnification. The trade-off is that images appear smaller.

The human eye is anatomically and functionally similar to a camera. The cornea and lens act as the camera lens to focus light, the pupil serves as the aperture controlling light intake, and the retina functions as the screen where the image is formed. This analogy is fundamental to understanding how vision works.

The retina acts as the screen or photographic film in the eye-camera analogy. Light focused by the lens falls on the retina, where photoreceptor cells (rods and cones) convert the optical image into electrical signals that the brain can process. This is exactly how a camera's film or sensor records an image.

Light is an electromagnetic wave that can travel through vacuum (empty space), which is why we receive sunlight. Sound is a mechanical wave that requires a material medium (solid, liquid, or gas) to propagate - it cannot travel through space. Both can be reflected and can bend around corners (diffraction), so the key distinction is the ability to travel through vacuum.

The iris is the colored part of the eye that contains muscles to control the size of the pupil. By adjusting pupil diameter, it regulates the amount of light entering the eye - dilating in low light conditions and constricting in bright conditions. The retina (option B) is the 'screen', and color discrimination is handled by cone cells in the retina (option C).

Myopia (nearsightedness) is a vision defect where distant objects appear blurry because the eye focuses images in front of the retina instead of on it. A person who cannot see clearly beyond 2 meters has myopia. Hypermetropia (farsightedness) is the opposite - difficulty seeing nearby objects. The 2m distance limit clearly indicates nearsightedness.

This is due to atmospheric refraction - light bends when passing through layers of air with different densities (which vary with temperature and altitude). This bending makes the moon appear slightly higher than its actual geometric position. The same principle explains why the sun is visible before it actually rises and after it sets.

Electric current in metallic conductors is the flow of electrons. Metals have free (delocalized) electrons in their atomic structure that can move when a voltage is applied. Electrons are negatively charged particles, opposite to positrons. Neutrons are neutral and found in nuclei, while photons are light particles with no charge.

Astigmatism is caused by an irregular curvature of the cornea or lens, making vision distorted at all distances. Cylindrical lenses have different curvatures in different directions and can correct this irregularity. Concave and convex lenses have uniform curvature, while 'plane lens' is not a standard optical term.

Hypermetropia (farsightedness) occurs when the eye is too weak or too short, focusing images behind the retina. A convex (converging) lens adds focusing power to bring images forward onto the retina. Concave lenses are for myopia, while plano-convex and plano-concave describe lens shapes, not the complete solution.

Resistance R = ρL/A where ρ is resistivity, L is length, and A is cross-sectional area. If L and A both double: R_new = ρ(2L)/(2A) = ρL/A = R. The resistance remains unchanged because the increase in length (which would increase resistance) is exactly offset by the increase in area (which decreases resistance).

A storage cell (like a lead-acid battery) stores electrical energy as chemical potential, but what it actually stores and delivers is charge. The 'charge' option refers to the separation and accumulation of charge that creates the potential difference. The cell itself is made of lead and other metals, but what's 'stored' is the charge separation.

Using the power formula P = VI, current I = P/V = 100W/220V = 0.4545...A ≈ 0.45A. This is the standard calculation for finding current from power and voltage ratings. Option A (2.2A) would be P/V = 484W, option B (1.1A) would be 242W, and option D (0.22A) would be 48.4W - none match the 100W rating.