6 LESSON_Q2

• Optics


  The study of light
• Classification of objects based on optical properties

  • Luminous
  • Nonluminous
  • Natural
  • Man-made
  • Opaque
  • Translucent
  • Transparent
• When light hits a completely opaque object, it cannot penetrate the object and its rays are bounced off the surface. This is what we call reflection.
• Laws of reflection


  • The angle of incidence is always equal to the angle of reflection
  • Both angles lie on the same plane
• Specular/Regular reflection


  Parallel incident rays are reflected regularly at the same angles
• Diffused/Irregular reflection


  Reflected rays are scattered in different directions
• Images in plane mirrors

  • Image formed has same size as the object
  • Image formed has same distance as object
  • Image formed seems to have a "left-right reversal" effect
  • Image formed is always upright
• Any person would need a mirror with length of at least half of his/her height for him/her to see his/her full-body image or reflection
• Multiple images formed by two plane mirrors

  1. Placing two plane mirrors at an angle

  2. Number of images depends on the angle between them
• Multiple images formed by two plane mirrors

  • Infinite images in an elevator with opposite reflective sides
  • 3 images when mirrors form a 90-degree angle
• Number of images formed by two plane mirrors at different angles

  • Angle between two plane mirrors
  • Number of images (N)
• Plane mirrors


  Two plane mirrors placed at an angle
• Number of images


  Depends on the angle between the two mirrors
• Image 1


  • Infinite images created by the reflective sides of an elevator
• Calculating number of images

  N = (3600/ϕ) - 1, where N = number of images and ϕ = angle between the two mirrors
• Image 2


  • Single object placed between two mirrors at 90 degree angle produces 3 images
• Angle between two plane mirrors

  • 45 degrees
  • 60 degrees
  • 75 degrees
• If you have two plane mirrors and a protractor at home, you can confirm the number of images by replicating the set-up
• Natural luminous object


  Object that can generate its own light
• Nonluminous object


  Object that cannot generate its own light
• Man-made luminous object


  Luminous object that exists because man invented it
• Opaque nonluminous object


  Object that does not allow light to pass through
• Translucent nonluminous object


  Object that allows some light to pass through, creating a vague or distorted image
• Transparent nonluminous object


  Object that allows light to pass through
• Reflection


  Phenomenon where a light ray bounces off the surface at a specific angle
• Law of reflection


  The angle of incidence is always equal to the angle of reflection
• Properties of images formed by plane mirrors

  • The image is virtual
  • The distance of the image from the mirror is the same as the distance of the real object to the mirror
  • The image has a right-left reversal effect
  • The orientation of the image is upright
• Periscope


  Device that allows a user to see objects that are not in their line of sight or blocked by an obstacle, using two plane mirrors angled at 45 degrees
• Curved mirrors


  Mirrors with a curved reflecting surface, including parabolic and spherical mirrors
• Concave mirror


  Smooth reflecting surface whose shape is "caved in" at the center
• Convex mirror


  Smooth reflecting surface whose shape is "bulging outwards" at the center
• Converging mirror


  Concave mirror that reflects parallel incident rays such that they converge at a real focus
• Diverging mirror


  Convex mirror that reflects parallel incident rays such that they diverge and form a virtual focus
• Center of curvature (C)

  Center of the sphere from which the concave or convex mirror's curve is derived
• Focus/Focal point (F)


  Point at which light rays meet for a concave mirror (real focus) or the point where virtual light rays traced backwards meet for a convex mirror (virtual focus)
• Principal axis


  Line that divides the mirror into two equal parts, passing through C, F and V
• Vertex (V)


  Point of intersection between the principal axis and the surface of the mirror
• Ray diagramming


  Technique to determine the qualities of images formed in curved mirrors by drawing select incident and reflected light rays
• 4 rays used in ray diagramming

  • P-F ray
  • V ray
  • F-P ray
  • C-C ray
• Location of object/image


  Beyond C, at C, between C and F, at F, between F and V, or inside the mirror