6.3 Optics

• What is a lens used for?

  To form an image by refracting light
• What are the two types of lenses?

  • Convex
  • Concave

  
• What happens to parallel rays of light in a convex lens?

  They are brought to a focus

  
• What is the point called where light rays converge in a convex lens?

  Principal focus

  
• What is a convex lens sometimes referred to as?

  Converging lens
• What does the focal length of a lens depend on?

  How curved the lens is
• How does the curvature of a lens affect its focal length?

  The more curved, the shorter the focal length
• What happens to parallel rays of light in a concave lens?

  They diverge from a point

  
• What is a concave lens sometimes referred to as?

  Diverging lens
• Where does the principal focus of a concave lens appear to be?

  From which rays appear to diverge

  
• What symbols are used to represent concave and convex lenses in diagrams?

  • Concave lens: diverging symbol
  • Convex lens: converging symbol

  
• Why is it important to remember the symbols for each type of lens?

  They are needed for ray diagrams in exams
• How can you remember which lens is converging or diverging?

  Convex lens = Converging

  
• What are the steps to draw ray diagrams for lenses?

  1. Identify the type of lens
  2. Draw rays from the object
  3. Determine where rays converge or appear to diverge
  4. Mark the image location

  
• What defines a real image?

  Formed when light rays converge and meet

  
• How can a real image be projected?

  Onto a screen or paper
• What is a characteristic of real images?

  They are always inverted
• What defines a virtual image?

  Formed when light rays appear to meet behind the lens

  
• Can a virtual image be projected onto a screen?

  No, it cannot be projected
• What is a characteristic of virtual images?

  They are always upright
• How are virtual images represented in ray diagrams?

  With dashed lines or one dashed and one solid line
• What are the characteristics of images formed by convex lenses?

  • Can be real or virtual
  • Real images are inverted
  • Virtual images are upright

  
• What are the characteristics of images formed by concave lenses?

  • Always virtual
  • Always upright
  • Always diminished
• What happens when an object is placed further than the focal length from a convex lens?

  A real image is formed

  
• What happens when an object is placed closer than the focal length from a convex lens?

  A virtual image is formed

  
• What is the first step in drawing a ray diagram for a convex lens?

  Draw a ray from the top of the object through the lens center

  
• What is the second step in drawing a ray diagram for a convex lens?

  Draw a ray parallel to the axis to the lens

  
• How do you determine the image location in a convex lens ray diagram?

  Where the two rays meet

  
• What is the nature of the image formed when the object is closer than the focal length in a convex lens?

  Virtual, magnified, and upright

  
• What is the first step in drawing a ray diagram for a concave lens?

  Draw a ray from the top of the object through the lens center

  
• What is the second step in drawing a ray diagram for a concave lens?

  Draw a ray parallel to the axis to the lens

  
• What is the nature of the image formed by a concave lens?

  Virtual, diminished, and upright

  
• What is the formula for magnification of a lens?

  • Magnification = Image height / Object height

  
• What are the characteristics of images produced by convex lenses compared to concave lenses?

  • Convex lenses: real or virtual, inverted or upright
  • Concave lenses: always virtual, always upright

  
• Why is it important to practice drawing ray diagrams?

  To gain confidence and accuracy in exams
• What tools should you use when drawing ray diagrams in an exam?

  Ruler and sharp pencil
• What does the formula triangle for magnification help with?

  Rearranging the magnification equation

  
• What is the first step in drawing a ray diagram?

  Draw a line from the top of the object
• What does the top of the image lie along in a ray diagram?

  It lies along the line drawn from the object
• What is the second step in drawing a ray diagram?

  Draw a line from the focal point through the top of the lens