• Characteristics of a convex lens
• Focal length of a convex lens
• Thin lens formula
• Types of images formed by a convex lens
• Image formation for different object positions

• 1/f = 1/v - 1/u
• Where f is the focal length, v is the image distance, and u is the object distance

• Real and inverted
• Virtual and upright
• Magnified and diminished
• Same size and erect

Image formation for different object positions:

• Object beyond the focal point:
  • Real, inverted, and diminished image formed
  • Example: Image formed by a convex lens when an object is placed at a distance greater than the focal length

Object at the focal point:

• No image formed

Object between the focal point and the lens:

• Virtual, upright, and magnified image formed
• Example: Image formed by a convex lens when an object is placed between the focal point and the lens

Focal plane in optical devices:

• Role of focal plane in telescopes
• Role of focal plane in cameras

Role of focal plane in telescopes:

• Focal plane is where the image formed by the objective lens is focused
• Allows for viewing or capturing the image

Role of focal plane in cameras:

• Focal plane is where the image formed by the lens is focused onto the film or image sensor
• Allows for capturing the image

Image formation by a concave lens:

• Characteristics of a concave lens
• Focal length of a concave lens
• Types of images formed by a concave lens
• Image formation for different object positions

Characteristics of a concave lens:

• Thin in the middle and thick at the edges
• Diverges light rays

Focal length of a concave lens:

• Negative value to indicate diverging lens
• Magnitude represents the degree of divergence

Types of images formed by a concave lens:

• Virtual, upright, and diminished

Image formation for different object positions:

• Object beyond the focal point:
  • Virtual, inverted, and diminished image formed

Image formation for different object positions (contd.):

• Object at the focal point:
  • No image formed

Object between the focal point and the lens:

• Virtual, upright, and magnified image formed

Ray diagrams for image formation:

• Construction of ray diagrams for convex and concave lenses
• Determining the position and nature of the image using ray diagrams

Construction of ray diagrams for convex and concave lenses:

• Use principal rays to determine the path of light

Determining the position and nature of the image using ray diagrams:

• Rays from the object to the lens are drawn
• Rays are refracted according to the rules of refraction
• Intersection of refracted rays gives the position and nature of the image

Examples of ray diagrams for image formation:

• Ray diagrams for convex lens with different object positions
• Ray diagrams for concave lens with different object positions

• Mirrors: Used for reflection and image formation
• Periscopes: Used for viewing in submarines and vehicles
• Kaleidoscopes: Creates colorful patterns using reflections
• Binoculars: Use lenses to magnify distant objects

Refraction of light

• Definition and concept
• Snell’s law
• Refractive index
• Examples of refraction of light

Definition and concept of refraction of light:

• Bending of light as it passes from one medium to another
• Caused by the change in speed of light

Snell’s law:

• n1 * sin(theta1) = n2 * sin(theta2)
• Where n1 and n2 are the refractive indices of the two media, and theta1 and theta2 are the angles of incidence and refraction, respectively

Refractive index:

• Measure of how much a medium can bend light
• Calculated as the ratio of the speed of light in a vacuum to the speed of light in the medium

Examples of refraction of light:

• Refraction of light in a glass prism
• Refraction of light in water
• Refraction of light in a camera lens

Refraction of light in a glass prism:

• Light entering a prism is refracted and separated into different colors (dispersion)

Refraction of light in water:

• Light entering water is refracted, making objects appear shifted

Refraction of light in a camera lens:

• Lens of a camera refracts light to form an image on the film or image sensor
• Allows for capturing the image

Lens formula:

• 1/f = 1/v - 1/u
• Where f is the focal length, v is the image distance, and u is the object distance

Types of lenses:

• Convex lens
• Concave lens

Convex lens:

• Thicker at the middle and thinner at the edges
• Converges light rays

Concave lens:

• Thin in the middle and thicker at the edges
• Diverges light rays

Image formation by a convex lens:

• Real and inverted image formed when the object is beyond the focal point
• Virtual and upright image formed when the object is within the focal point

Image formation by a concave lens:

• Virtual, upright, and diminished image formed for all object positions

Power of a lens:

• Measure of the ability of a lens to converge or diverge light
• Calculated as the reciprocal of the focal length

Power of a lens formula:

• P = 1 / f
• Where P is the power of the lens in diopters, and f is the focal length in meters

Lens combinations:

• Two lenses can be combined to form different optical systems
• Examples include microscope, telescope, and camera

Microscope:

• Uses multiple lenses to magnify small objects

Telescope:

• Uses multiple lenses to magnify distant objects

Camera:

• Uses lens combinations to focus and capture images

Magnification:

• Measure of the size of an image compared to the size of the object
• Calculated as the ratio of the image height to the object height

Magnification formula:

• Magnification (M) = h2 / h1
• Where h2 is the image height and h1 is the object height

• Eyeglasses: Correct vision by converging or diverging light
• Contact lenses: Correct vision by conforming to the shape of the eye
• Fiber optics: Transmit light signals for communication and data transfer
• Holography: Create 3D images using interference patterns