13.4 Lenses and Image Formation

• Concave lenses are thicker in the middle and narrower at the edges.

  False
• What type of image is formed by a concave lens?

  Virtual, upright, smaller
• Concave lenses diverge light rays to form a virtual image.
• What is the focal length of a convex lens considered?

  Positive
• Concave lenses have a negative focal length.


  True
• In sign conventions, a positive object distance indicates the object is on the same side of the lens as the incoming light.
• Match the sign of magnification with the image property:

  Positive magnification ↔️ Upright image

  Negative magnification ↔️ Inverted image
• What are the two main types of lenses?

  Concave and convex
• Convex lenses converge light rays.
• The principle of refraction through lenses depends on the shape of the lens.

  True
• Steps in the refraction of light through a lens

  1️⃣ Light ray enters the lens

  2️⃣ Light is bent or refracted

  3️⃣ Light exits the lens
• The focal point is where parallel light rays converge after passing through a convex lens.
• What is the purpose of sign conventions in lens calculations?

  Determine image properties
• A concave lens has a positive focal length according to sign conventions.

  False
• What is the focal length of a concave lens according to sign conventions?

  Negative
• A convex lens can form both real and virtual images.


  True
• Correctly using the thin lens equation is crucial for analyzing image properties formed by lenses.


  True
• The thin lens equation is \frac{1}{f}
• What are the two main types of lenses?

  Concave and convex
• Steps in light refraction through a convex lens

  1️⃣ Light enters the lens

  2️⃣ Light is bent or refracted

  3️⃣ Light converges at the focal point
• The principle of refraction states that light is bent or refracted
• The focal length of a lens is the distance from the lens to the focal point
• Match the lens type with its focal length sign:

  Concave Lens ↔️ Negative

  Convex Lens ↔️ Positive
• What is the sign of the focal length for a convex lens?

  Positive
• Match the lens type with its image properties:

  Concave Lens ↔️ Virtual, upright, smaller

  Convex Lens ↔️ Real or virtual, inverted or upright, larger or smaller
• Sign conventions for lenses are important in determining image properties.


  True
• For concave lenses, the image formed is virtual and on the same side as the object.


  True
• For convex lenses, the focal length is positive
• The focal length of a convex lens is always positive.


  True
• A positive magnification indicates an upright image.
• What does a negative magnification value indicate about the image?

  Inverted
• Which lens type always forms a virtual image?

  Concave
• What happens to the central ray as it passes through the lens?

  It remains undeviated
• Arrange the three principal rays in the order of their description during ray tracing:

  1️⃣ Parallel ray

  2️⃣ Focal ray

  3️⃣ Central ray
• The key to effective ray tracing is identifying and drawing the principal rays
• A ray passing through the center of the lens continues unrefracted
• A focal ray is a ray passing through the focal point that refracts parallel to the principal axis.


  True
• The parallel ray in a concave lens diverges after passing through the lens
• What happens to a parallel ray in a concave lens after passing through it?

  It diverges
• A parallel ray in a convex lens converges at the focal point on the opposite side of the lens