Converging and Diverging Lenses

• What is a lens used for?

  To form an image by refracting light

  
• What are the two types of lenses?

  Convex and concave lenses

  
• How do parallel rays behave in a converging lens?

  They are brought to a focus along the principal axis

  
• What is the focal point in a converging lens?

  The point where light rays converge

  
• What is the focal length in a converging lens?

  The distance from the lens to the focal point
• How does the curvature of a lens affect its focal length?

  More curvature results in a shorter focal length
• What does a shorter focal length indicate about a lens?

  The lens is more powerful

  
• What sign is the focal length for a converging lens?

  Positive

  
• What types of images can lenses produce?

  Real or virtual images

  
• What are the characteristics of real and virtual images?

  Real Image:

  • Light converges towards a focal point
  • Always inverted
  • Can be projected onto a screen

  
  

  Virtual Image:

  • Light diverges away from a focal point
  • Always upright
  • Cannot be projected onto a screen
• What is the first rule for constructing ray diagrams for converging lenses?

  Rays through the principal axis pass undeviated

  
• What is the second rule for constructing ray diagrams for converging lenses?

  Rays parallel to the principal axis pass through the focal point

  
• What is the third rule for constructing ray diagrams for converging lenses?

  Rays through the focal point emerge parallel to the principal axis

  
• How can images formed by lenses be described?

  • Nature: Real or virtual
  • Orientation: Inverted or upright
  • Size: Magnified, diminished, or same size

  
• What happens to the image when an object is placed further than 2 focal lengths from a converging lens?

  The image is real, inverted, and diminished

  
• What happens to the image when an object is placed at exactly 2 focal lengths from a converging lens?

  The image is real, inverted, and the same size

  
• What happens to the image when an object is placed between 1 and 2 focal lengths from a converging lens?

  The image is real, inverted, and magnified

  
• What happens to the image when an object is placed less than the focal length from a converging lens?

  The image is virtual, upright, and magnified

  
• What are the steps to draw a ray diagram for a converging lens?

  1. Draw and label the principal axis and lens
  2. Mark and label the focal points
  3. Draw and label the object at a distance greater than the focal length
  4. Draw a ray through the optical center
  5. Draw a second ray parallel to the principal axis
  6. Draw the continuation of the ray through the focal point
  7. Draw and label the image where the rays meet

  
• How do parallel rays behave in a diverging lens?

  They diverge from the principal focus

  
• What is another name for a diverging lens?

  Concave lens

  
• What is the focal length in a diverging lens?

  The distance from the lens to the focal point
• What sign is the focal length for a diverging lens?

  Negative
• What are the characteristics of images formed by diverging lenses?

  • Nature: Virtual
  • Orientation: Upright
  • Size: Diminished
  • Position: Same side as the object

  
• What are the steps to draw a ray diagram for a diverging lens?

  1. Draw a ray from the top of the object through the center of the lens
  2. Draw a ray from the top of the object parallel to the axis
  3. Draw the continuation of the ray diverging from the focal point
  4. The image is where the rays appear to meet

  
• What should be included in a ray diagram for a diverging lens to gain full marks?

  Object, image, and principal focus must be labeled

  
• What is the behavior of rays incident on the center of a diverging lens?

  They do not change direction
• What happens to rays parallel to the principal axis in a diverging lens?

  They appear to come from a virtual focus

  
• What is the significance of dashed lines in ray diagrams for diverging lenses?

  They indicate the direction of diverging rays

  
• What are the examiner tips for drawing ray diagrams?

  • Use correct symbols for lenses
  • Label all important parts clearly
  • Ensure rays are accurately drawn