Optics (ray and wave)

• In reflection:

  1. No change in frequency
  2. No change in speed
  3. No change in wavelength
  4. change in phase by 180 and direction
• Change in direction of light by angle of 180-2x

  where x= angle of incidence
• Focal length of mirror is independent of medium
• m= f/f-u
• m= f-v/f
• The image formed by the concave lens is real, inverted, magnified, and located beyond the lens.
• The image formed by the convex lens is virtual, erect, diminished, and located behind the lens.
• Concave mirrors are converging, diverging mirrors are concave
• f of plane mirror is infinite
• plane mirror form virtual and erect image
• The bending of light ray depend on:

  1. Change is speed
  2. Angle of incident ray


  Angle of incident is greater amount of refraction will be more
• if the light is entering new substance at 90 degree from surface it will slow down but no change in diretion.
• In refraction the light speed, wavelength and direction changes but no change in frequency as it is the characterstic property of source of light.
• speed is directly proportional to wavelength
• rarer to denser- speed decreases ; wavelength decreases by same amount , bends towards normal ; i > r
• denser to rare - speed increases; wavelength increases by same amount , bends away from normal ; i < r
• wavelength of light is inversely proportional to refractive index
• focal length of lens depend on radius of curvature of both surface and refractive index of lens and surrounding
• Magnification is inversely proportional to the focal length of the lens
• Focal length of objective lens is less than focal length of eye lens in microscope
• Angular Magnification- ratio of angle formed by the image(B) with eye of observer when the final image is formed at least distance of distinct vision or infinity to the angle formed by object(a) with eye of observer when object is assumed to be placed at least distance of distinct vision/infinity
• Near point- image at least distance of distinct vision (D=25)
• Normal Adjustment- image at infinity
• For greater magnification in telescope objective lens is adjusted just near the eye lens
• In telescope objective lens has large focal length than the eye lens
• Large magnification can be achieved if the focal length of objective>>>>> than eyepiece
• For minimum deviation vale of i = e
• in minimum deviation refracted light is parallel to the base of the prism
• critical angle is inversely proportional to refractive index
• critical angle is directly proportional to wavelength
• condition for TIR:

  1. Light travel from denser to rarer medium
  2. angle of incidence greater than critical angle
• with change in medium focal length change
• In water focal length increases by 4 times of lens in ari
• Focal length, f cut vertical axis- both halves will have 2f focal length
• half length painted black no change in focal length but brightness of image(intensity) decreases
• If we reverse telescope it will not behave as microscope coz focal length of objective is bigger
• wavelength of radiation is inversely proportional to angle of deviation
• In fiber optics cladding has lower refractive index than core