test 4

• Hubble space telescopes show clearer images than Earth-based telescopes due to the absence of an atmosphere in space.
• Light exhibits four properties: it is a form of energy, travels in straight lines, can reflect, and can refract.
• Telescopes enlarge images and collect light from distant objects.
• Refracting telescopes use two lenses.
• Reflecting telescopes use a curved (concave) mirror and a lens.

Light Rays

• Light travels in straight lines called light rays.
• Light rays end with an arrow to indicate direction.
• Light rays travel away from a light source in every direction.
• The closer to the light source, the brighter the light; the further away, the darker. This change in light amount is called intensity.

Material Interactions

• Transparent materials transmit light, allowing it to pass through.
• Translucent materials allow some light to pass through.
• Opaque materials do not allow light to pass through.
• Luminous objects produce light, while non-luminous objects cannot.

Reflection

• Regular reflection occurs when parallel rays reflect off a smooth surface in a predictable pattern.
• Diffuse reflection occurs when parallel rays reflect off a rough surface and scatter in different directions.

Law of Reflection

• The normal is an imaginary line perpendicular to the mirror at the point of reflection, used for measuring angles.
• The angle between the incident ray and the normal is called the angle of incidence.
• The angle between the reflected ray and the normal is called the angle of reflection.
• The law of reflection states that the angle of incidence is equal and opposite to the angle of reflection.

Curved Mirrors

• Concave mirrors curve inward like a bowl.
• Parallel rays that hit a concave mirror reflect and converge at a common point called the focal point (apex).
• An object far from a concave mirror produces an inverted and smaller image.
• The closer an object is to the focal point of a concave mirror, the larger the reflected image appears.
• When an object is placed between the focal point and a concave mirror, the image becomes upright and larger.
• Convex mirrors curve outward.
• Convex mirrors spread out light rays instead of collecting them.
• The focal point of a convex mirror is located behind the mirror.
• Reflected images in a convex mirror always appear upright and smaller.

Refraction

• Light in a vacuum travels at about 300,000 km/s.
• Light slows down when passing from a less dense to a more dense medium.
• Light speeds up when passing from a more dense to a less dense medium.
• When light travels at an angle from one medium to another, it bends or refracts.
• The more dense the medium, the more the light will slow down and refract.
• Light rays bend toward the normal when entering a more dense medium at an angle.
• Light rays bend away from the normal when entering a less dense medium at an angle.

Lenses

• Concave lenses are thinner in the middle than at the edges, while convex lenses are thicker in the middle.
• A magnifying glass uses a convex lens.
• Parallel rays traveling through a convex lens refract toward each other, creating a focal point.
• Parallel rays traveling through a concave lens refract so the light rays spread out.
• If an object is far away from a convex lens, the image will be inverted and smaller.
• The closer an object gets to the focal point of a convex lens, the larger the image appears.
• If an object is placed between the focal point and a convex lens, the image becomes upright and larger.
• An image created from a concave lens will always appear upright and smaller.

Key Scientists and Their Contributions

• Ole Romer: First measured the speed of light.
• Albert A. Michelson: Measured the speed of light more accurately.
• Archimedes: Thought he could burn enemy ships with reflected light from the sun.
• Pythagoras: Thought beams of light came from our eyes.
• Euclid: Came up with the law of reflection.
• Al Haytham: Accurately described how vision works and diagrammed the eye.
• Galileo: Perfected the telescope and made discoveries such as the moons of Jupiter.
• The Jansens: Built the first microscope in 1595.
• Van Leeuwenhoek: Used the microscope to discover "little animalcules".

Definitions

• Light Year: A unit used to measure astronomical distances.
• Ray: a straight line with an arrow on the end that represents the path of a beam of light.
• Transmitted: When light travels in straight lines until it strikes a surface, it is either transmitted, reflected, or absorbed.
• Translucent: Some light passes through and some is blocked like a frosted class window
• Transparent: Light passes through/ transmits
• Opaque: A surface that permits on light to pass through
• Luminous: Objects that give off a light
• Refraction: is caused by changes in the medium