Ray Optics

• Convex mirror~ Diverging

  Covex lens~ Converging

  Concave mirror~ Converging

  Concave lens~ Diverging
• Focal point is where parallel rays meet at one point
• The focal length is the distance from the centre of curvature to the focus
• Principal axis is an imaginary line passing through the centre of curvature, the optical centre and the pole (centre)
• Ray infront of mirror~ real(solid line is used)

  Ray behind of mirror~imaginary(dash line is used)
• Autocollimation

  It is a condition where object and image lie at the same position(C) and the height of image is same as that of the object.
• Real images are formed when light rays converge on a screen or film. They can be projected onto a screen or viewed with the eye.
• Virtual images cannot be projected onto a screen or filmed because they do not actually exist. Instead, they appear to come out of the surface of the mirror.
• A convex lens has a positive power and forms a virtual, erect image. A concave lens has negative power and forms a virtual, upright image.
• A concave lens has negative focal length and forms virtual images.
• A convex lens has positive focal length and forms real images.
• Concave mirrors have negative focal lengths and form virtual images.
• Myopia: shortsightedness

  ~near object are clear, far objects are blurred

  ~concave lens is used

  ~f=-ve
• Hypermetropia: farsightedness

  -far objects are clear, near objects are blurred

  -convex lens is used

  f=+ve
• What is the branch of physics that deals with the study of light and its behavioral properties?

  Optics
• What are some phenomena studied in optics?

  Reflection, refraction, interference, diffraction, and polarization of light

  
• What part of the electromagnetic spectrum helps us see various objects?

  Visible light

  
• What is the wavelength range of visible light?

  Approximately between 400 Å and 7500 Å

  
• How is a ray of light defined?

  A straight line drawn in the direction of propagation of light

  
• What is a beam of light?

  A bundle of rays

  
• What are the two types of optics?

  1. Ray Optics

  • Deals with the particle nature of light
  • Explains reflection and refraction
  • Assumes dimensions of objects are much larger than the wavelength of light

  2. Wave Optics

  • Deals with the wave nature of light
  • Explains interference and diffraction
  • Proposed by Christian Huygen in 1679

  
• What are luminous objects?


  Objects that give off their own light
• Give an example of a luminous object.


  Sun, lighted candle, or red hot iron
• What are non-luminous objects?


  Objects that do not give off their own light but reflect other’s light
• Provide an example of a non-luminous object.

  Moon, table, chair, cat, or dog
• What are incandescent objects?


  Luminous objects that can produce light as a result of being hot
• Give an example of an incandescent object.


  Sun, lighted candle, or red hot iron
• What is reflection in terms of light?

  A bouncing of light back in the same medium after striking a reflecting surface

  
• What are the two types of reflection?

  Regular (specular) reflection and irregular (diffuse) reflection

  
• Describe regular (specular) reflection.


  • Reflection from a smooth surface
  • All reflected rays go in one direction
  • Used in telescopes

  
• Describe irregular (diffuse) reflection.

  • Reflection from a rough or irregular surface
  • Reflected rays scatter in many directions
  • Illuminates the whole surface

  
• What is the law of reflection regarding the angle of incidence and angle of reflection?

  Angle of incidence (��) is equal to the angle of reflection (𝑟), i.e., 𝑖 = 𝑟

  
• What is the definition of the angle of incidence?


  The angle between the incident ray and the normal
• What is the definition of the angle of reflection?

  The angle between the reflected ray and the normal

  
• What is the normal in optics?

  An imaginary line drawn perpendicular to the reflecting or refracting surfaces

  
• What is the angle of deviation?

  The angle deviated by a light ray from its original path

  
• How is the angle of deviation related to the angles of incidence?


  It is defined by the equation \( \delta = 180° - 2\theta \)
• What is the relationship between angles in the equation \( \theta + \delta + \theta = 180° \)?

  It shows that the sum of the angles in a straight line is 180°
• What is a mirror?

  • A surface that reflects light
  • Produces real or virtual images
  • The object is the source of incident rays, and the image is formed by reflected rays

  
• What are the two main types of mirrors?

  1. Plane Mirrors

  • Flat, smooth reflective surface
  • Always forms a virtual image that is upright and the same size as the object

  2. Spherical Mirrors

  • Reflecting surface is part of a sphere
  • Can form either real or virtual images