Light: Reflection and its Laws

Basics of Light

• Light is a form of energy that allows sight.
• Light travels in straight lines.

Reflection of Light

• Reflection occurs when light bounces back in the same medium after hitting a surface.
• Incident Ray: The ray of light striking the surface.
• Reflected Ray: The ray of light bouncing off the surface.
• Normal: A line perpendicular to the surface at the point of incidence.
• Angle of Incidence: The angle between the incident ray and the normal.
• Angle of Reflection: The angle between the reflected ray and the normal.
• Angles are measured from the normal.

Types of Reflection

• Regular Reflection: Occurs on smooth, polished surfaces; parallel incident rays remain parallel after reflection, forming clear images.
• Diffused Reflection: Occurs on rough surfaces; parallel incident rays do not remain parallel, objects are visible but images aren't clear.
• Diffuse reflection follows the laws of reflection.

Laws of Reflection

• The angle of incidence equals the angle of reflection (i = r).
• The incident ray, the reflected ray, and the normal all lie in the same plane.

Image Formation by Plane Mirrors

• Size: Image size equals object size.
• Distance: Object distance equals image distance behind the mirror.
• Nature: Images are erect.
• The image is laterally inverted (left and right are reversed).
• Type: Images are virtual, appearing behind the mirror where light rays seem to meet, and cannot be projected onto a screen.
• Virtual Image: An image formed where light rays only appear to meet; cannot be projected onto a screen.

Multiple Reflections

• Multiple images are created when light reflects off two or more mirrors set at an angle.
• Number of images is calculated using 360/Θ - 1.
• Mirrors positioned at an angle can produce multiple reflections.
• Multiple reflections allow viewing of objects not in direct line of sight.

Reflection and Refraction Applications

• Periscope: Uses two mirrors at 45-degree angles to see over obstacles.
• Kaleidoscope: Uses multiple mirrors to create repeating patterns.
• Optical Fibers: Use multiple reflections to transmit light signals long distances.

Dispersion of Light

• Dispersion splits white light into its constituent colors (the visible spectrum).
• Rainbows: Natural dispersion occurs as water droplets act like prisms.
• Compact Discs (CDs): Exhibit dispersion, creating rainbow-like effects.
• Prism: Separates white light into colors; red bends the least, violet bends the most.

Human Eye

• Cornea: The outermost protective layer where maximum light bending occurs.
• Pupil: The hole in the center of the eye allowing light to enter.
• Eye Lens: Bends light to help form an image.
• Ciliary Muscles: Control the shape of the eye lens for focusing.
• Retina: The screen at the back of the eye where images are formed.
• Optical Nerve: Carries the image from the retina to the brain.
• Blind Spot: The area where the optical nerve leaves the eye, lacking photoreceptors.

Pupil Size

• Pupil size changes with light levels.
• The pupil gets smaller in bright light.
• The pupil gets larger in dim light.

Defects in Vision

• Myopia: Nearsightedness, near objects are clear, but distant objects are blurry.
• Hyperopia: Farsightedness, far objects are clear, but near objects are blurry.
• Cataract: The eye lens becomes opaque, causing blurriness; surgery is needed.

Eye Care

• Nutritional foods with Vitamin A are good for eye health.
• Avoid rubbing eyes.
• Maintain a 25 cm reading distance.

Braille System

• Braille is a tactile reading/writing system for the visually impaired, invented by Louis Braille.
• It uses raised dots to represent letters and numbers.