Subject: Science

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Lesson Info

  • Notes 4
  • Videos 25
  • Exercises 40
  • Practice Test 18
  • Skill Level Medium


On completion of this lesson, students should be able to:

  • Explain the laws of refraction.
  • Draw the ray diagram of concave and convex lenses.
  • Show the uses of lenses in our daily life.
  • Explain the defects of vision and their remedy.
  • Explain the working of optical instruments such as camera, telescope and microscope.



The phenomenon of bending of light as it passes from one medium to another medium is called refraction of light. The refraction is caused due to change in velocity of light as it passes from one medium to another medium. This note contains different definitions regarding a lens and also shows how light bends when it passes through concave or convex lens.

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Microscope and Telescope

The instrument, which are used to produce an image of an object by using a lens or a combination of lenses, are called optical instrument. Examples are a Photographic camera, microscope, telescope, etc. This note explains the normal working mechanism of telescope and microscope and briefly explains about the photographic camera: is an optical instrument that is used to record a permanent image of an object on a photographic film. Learn More

Human Eye

Conjunctive, ciliary body, aqueous, iris, cornea, pupil, lens, optic nerve, macula, retina, sclera, vitreous, etc. are the parts of human eye. This note has information about, the working principle of human eye and also the defects arise when the proper focus of light is not at the retina. Learn More

Magnification and Image

Magnification of a lens is defined as the ratio of the height of the image to the height of the object. The images can be of two types. An image that can be obtained on a screen is called a real image. An image which cannot be obtained on a screen is called a virtual image. 

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