Understanding Light, Microscopes, and Telescopes

• Light is a visible form of energy
• Light can be transformed into thermal, electrical, and chemical energy.

Evolving Understanding of Light

• Early theories lacked proof and understanding of energy forms.
• Knowledge of invisible energy forms gives a better picture of light's nature.
• Light is a visible form of energy transmitted through substances.
• Light is reflected, refracted, and absorbed by various surfaces.
• Luminous objects emit light; non-luminous ones are visible through reflection.
• Light intensity affects the energy a surface receives.

Microscopes and Telescopes

• Microscopes and telescopes enhance human vision for minute and distant objects.
• Both use high-powered lenses.
• Microscopes enable study of cells and microscopic organisms.
• Telescopes facilitate astronomy, with military applications.

Ray Model of Light

• Describes light's path and behavior upon hitting surfaces.
• A ray represents a light beam's path.
• Transparent substances transmit light for clear images, though images may appear distorted.
• Translucent substances refract light for seeing shapes, but no clear images.
• Opaque substances block light; reflective surfaces bounce it back. Non-reflective convert light to other forms of energy.

Shadows

• Opaque objects block light, forming shadows.
• Shadow size depend on the opaque object's proximity to the light source.

Natural Light

• Sun: Nuclear fusion creates abundant, inexpensive light.
• Bioluminescence: Chemical reactions in living beings (e.g., fireflies) produce light.

Artificial Light

• Incandescence: Heating a substance to emit visible light and transforms electrical energy into thermal, then light energy
• Fluorescence: a two-stage process to emits visible light transforming light into energy.
• Phosphorescence: Absorb light energy and continue to emit it long after the energy source has stopped
• Chemiluminescence: Chemical reactions transform chemical energy into light.

Refracting Telescopes

• Objective lens collects and minimizes distant light to an image.
• The eyepiece lens magnifies the tiny image.

Reflecting Telescopes

• Use primary mirrors to magnify distant images.
• Reflected image is viewed through an eyepiece lens.

Binoculars

• Uses mirrors to bounce images back and forth for viewing
• Achieve greater magnification within a compact design.

Reflection

• Dense, smooth surfaces reflect in predictable ways, forming visible images.
• Rough surfaces cause erratic reflection, showing the object, but without an image.
• The angle of incidence equals the angle of reflection.

Refraction

• Refraction alters light direction via a substance with a different density.
• Particle density affects light speed; less density means faster travel.
• Fast travel = less density and slow travel = more density
• Light bends towards the normal when moving from less to more dense medium, away in reverse
• Optical illusions exist due to refraction.

Lenses

• Lenses = curved transparent material (plastic/glass) that cause light to bend (refract)
• Concave lenses diverge (spread out) light rays.
• Convex lenses converge (bring together) light rays.
• Thicker lenses cause more divergence/convergence.
• Double concave lens is thin near the center making light spread out as it passes through the lens
• Double convex lens is thicker near the center causing that light to converge more when the light passes through.

Refracting Telescopes

• The objective lens takes a large field and shrinks it to a tiny image
• The eyepiece works like a magnifying glass and enlargens the image

How Vision Works

• Cornea/lens focuses light on the retina.
• Iris controls pupil size, regulating light intake
• The Retina, with rods/cones, collects incoming light and makes it visible.
• Jelly-like substance helps retina to capture the image effectively
• Brain interprets electrical impulses that are sent through electrical signals

Digital Cameras

• Digital cameras record points of light
• Each point of light it records is called a pixel
• Pixels form digital image, with variations creating detail.

Eye Specialization

• Eye specialization is genetic adaption based on success, purpose, lifestyle, and environment

Organisms Vision Examples

• Fruit Flies: Compound eyes gather information from hundred of light sensitive units
• Frogs & Toads: Have large field of view and can adjust their focus

Vision Correction with Lenses

• Far-Sighted Vision: Can see far but has trouble seeing close and uses a convex lens to help
• Near-Sighted Vision: Can see objects close up uses a concave lens to help

Laser Eye Surgery

• Laser eye surgery reshapes/thins the cornea for proper focus.