Refraction of Lens

Introduction to Lens

• A lens is a transparent refracting medium.
• Lenses are found in various forms around us:
  • Mobile camera
  • Glasses
  • Microscope
  • Telescope
  • Video camera

Functions of Lens

• A lens bends light.
• The speed of light changes when moving from air to glass.

Types of Lenses

1. Convex Lens (Converging Lens)
   • Identification:
     • Thicker in the middle, thinner at the edges.
   • Function:
     • Converges light rays to a point.
   • Example:
     • Glasses (if the middle part is thick).
2. Concave Lens (Diverging Lens)
   • Identification:
     • Thinner in the middle, thicker at the edges.
   • Function:
     • Diverges light rays.
   • Example:
     • Glasses for nearsightedness.

Important Parts of a Lens

• Optical Center:
  • Light rays pass through this point without bending.
• Focal Point:
  • The point where light rays converge.

Laws of Refraction

1. First Law:
   • Light rays passing near the optical center do not bend.
2. Second Law:
   • Light rays parallel to the principal axis pass through the focal point.
3. Third Law:
   • Light rays passing through the focal point become parallel.

Image Formation

• Real Image:
  • Light rays actually meet.
  • Always inverted.
• Virtual Image:
  • Light rays do not actually meet.
  • Always upright.

Lens Formula

• The lens formula:
  • 1/v - 1/u = 1/f
  • "u" (distance of the object), "v" (distance of the image), "f" (focal length).

Magnification

• The ratio of the image to the object.
• [ \text{Magnification} = \frac{h_i}{h_o} = \frac{v}{u} ]
  • ( h_i ) = height of the image
  • ( h_o ) = height of the object

Power of Lens

• Unit of power: Diopter (D)
• Formula for power:
  • [ P = \frac{1}{f} ]
  • Measure "f" in meters.

Applications

• Uses of lenses in many places such as:
  • Camera
  • Projector
  • Microscope
  • Telescope
• Lenses are important in our daily life, such as glasses for the eyes.

Conclusion

• Lenses are crucial in bending light and are used in various devices.
• Knowledge of lens types and their functions is essential in science.