Section outline

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      Important Terms:

      1. Light is a form of energy that enables us to see.

      2. Reflection of Light is change in direction of light when it falls on a shiny surface.

      3. Mirror any polished or shiny surface that reflects light.

      4. Object is the thing in front of the mirror.

      5. Image is the object which appears behind the mirror.

      6. Real image is an image which can be obtained on a screen.

      7. Virtual image is an image which cannot be obtained on a screen. 

      8. Erect image is an image that is upright or straight as the object.

      9. Inverted image is an image that is upside down or rotated 180o.

      10. Concave mirror: When the reflecting surface of the spherical mirror is concave (i.e. curved inward).

      11. Convex Mirror: When the reflecting surface of the spherical mirror is convex (i.e. curved outward).

      12. Convex or converging lens are those lenses which are thicker in the middle than at the edges.

      13. Concave or diverging lens are those lenses which are thinner in the middle than at the edges.

      14. Newton's disc is a circular disc with colored segments that appear white when rotated rapidly.

       

      Key points:

      1. Light travels along straight line.

      2. White light is composed of seven colours.

      3. A rainbow consists of seven colours - red, orange, yellow, green, blue, indigo and violet.

      4. A prism splits a beam of sunlight into seven colours.

      5. A convex lens converges (bends inwards) the light falling on it.

      6. A concave lens diverges (bends outwards) the light falling on it.

    • Mind map of Light:

    • Quick Revision Notes

      1. Reflection of Light takes place on the following surfaces:

      • Mirror
      • Water
      • An shining surface like stainless steel plate or spoon.
      2. Types of Images:
      • There are two types of images real & virtual.
      • Real image can be obtained on the screen whereas virtual image cannot be obatined on screen.
      3. Types of Mirror:
      • Mirrors are of two types: plain & spherical.
      • Shperical mirror are of two types: convex & concave.
      Mirror Image Uses
      Plain Virtual, Erect & Laterally inverted Daily use mirrors, periscopes, solar cookers, kaleidoscope, torch lights, etc.
      Same size as object
      At same distance as the object 
      Concave

      Real & inverted

      Virtual, erect & magnified when object close to mirror

      		 Headlights of cars & scooters
      Dentists to see an enlarged image of the teeth
      Reflectors of torches
      Doctors to examine eyes, ears, nose & throat
      Convex
      		 Erect, virtual & smaller in size Rear view & side view mirrors in automobiles
      4. Types of Lenses:

      Lense Image Uses
      Convex or Converging

      Real & inverted

      Virtual, erect & magnified when object close to mirror

      		 Magnifying glass, eyeglasses (for farsightedness), microscopes, telescopes, cameras, etc.
      Concave or Diverging
      		 Erect, virtual & smaller in size Eyeglasses (nearsightedness), peepholes, binoculars, flashlights, cameras, etc.
      5. Dispersion of light:
      • When sunlight or white light splits into seven colours it is called dispersion of light.
      • These colours are red, orange, yellow, green, blue, indigo and violet.
      • This happens when light passes through a prism or soap bubbles or rain drops (forming rainbow) or reflected from CD surface.