Light and Optics Topic 2

• • Ways that light can reflect is off of mirrors or shiny objects.
• • Glare: light reflected off of glass or anything that is not a mirror.
• Refraction occurs when the speed of light changes as it passes from one medium to another, causing its path to change direction.
• When light enters a denser medium (slower), it bends towards the normal line.
• Luminous: objects that produce light, such as stars, galaxies, and the sun.
• Non-luminous: No light is emitted, and the light can be reflected or absorbed.
• The closer we are to the source, the more intense it is
• If an object is between the light source and our eyes, we see this lack of light as a shadow

  
• A shadow is formed by blocking out part of the light rays coming from the light source
• Regular Reflection: when parallel rays hit a smooth surface and all the rays reflect at the same angle

  A) Plane Mirror
• Plane mirror: A flat sheet of glass with a shiny back surface used to form images
• Light rays entering a convex lens converge at one point called the focal point (F).
• Concave mirrors: Convex mirrors have a curved surface facing away from the observer, while concave mirrors have a curved surface facing towards the observer.
• Concave mirrors have their focal point on one side of the mirror (convex)
• When light enters a concave lens, it diverges or spreads apart.
• The image produced by a concave mirror can be real or virtual depending on its position relative to the focus.
• Objects placed beyond the principal focus of a concave mirror produce real images that are larger than their original sizes.
• Diffused Reflection: when a parallel ray hits a rough surface and all rays reflect at different angles

  
• Law of Reflection: when a light ray hits a plane mirror at any angle, it is reflected at the same angle.

  
• Concave Mirror: light rays reflected off of it converges. If the object is between the focal point and the mirror, it is upright and enlarged. If it is far away from the focal point, it is shown as upside-down and small.
• An example of a concave mirror is a reflecting telescope.
• Concave Mirror:

  
• Convex Mirror:


  Light rays reflected off of it diverge.

  
• Refraction:

  • When a light ray hits where two different substances meet(interface) at an angle (it will also change direction)
  • The angles are going to vary based on the substance the light is passing through
  • As the angle of incidence increases, so does the angle of refraction
• Refraction:

  Air to Water

  • when light travels from a less dense medium to a denser medium, the light will bend towards the normal

  
• Denser Material to Less Dense

  • when light exits a denser medium and moves into a less dense medium, the light will bend away from the normal

  
• Concave Lens:

  • when light rays pass through a concave lens it diverges
• Concave Lens: they are used for glasses and contact lenses

  
• Convex Lens: when light rays pass through it, the light rays converge or come together

  • ex. eyeball, microscope, and projector

  
• Florescent Light

  • A glass tube filled with a small amount of gas (ex. Mercury vapor)
  • The inside of the bulb is coated with a white powder called phosphor
  • As electricity passes through the bulb, the gas in the bulb will emit ultraviolet radiation
  • This strikes the phosphor, which glows, and emits visible white light
  • This emission is called fluorescing
• Incandescent Light

  • Thin wire inside is called the filament
  • When we turn our lights on electrical energy flows through the filament, thus heating it up to extremely high temperatures
  • As the filament is heating up, it glows “white hot” creating light
  • Light we see is the glowing filament
  • Produces about 95% heat and 5% light
  • Electrical energy-thermal energy-visible light energy
• Phosphorescent Light

  • Process in which a substance emits light AFTER it has absorbed ultraviolet radiation
  • They can store energy from the radiation, then emit light after the source of radiation has stopped
  • Glow in the dark items are phosphorescent
  • Can be re-energized by being held under a lamp for a few minutes 
  • More efficient than incandescent bulbs, but still release up to 80% of their energy
  • Last much longer than incandescent bulbs
• Chemiluminescent Light

  • Light energy that is released by a chemical reaction
  • Example: Glow Sticks
• LED – Light Emitting Diode

  • Considered very efficient and have a much longer lifespan than incandescent and fluorescent lights
  • Light is produced by the movement of electrons – no heat is required
• Bioluminescence Light

  • The ability of certain organisms to produce light by a chemical reaction
  • Photophore light producing organ 
  • Very efficient because it gives off no waste heat (called cool light)
  • Can also be caused by a light producing bacteria
  • Ex. Black Sea Dragon