Light

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A light lesson for grade 7 base in Checkpoint physics book.

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Light

  1. 1. By : Firman
  2. 2.  Luminous object is a object that can shining by itself or emit light by itself. Example : Fire , sun , lamp.
  3. 3.  Non luminous object is a object that cannot emit light itself they can only reflecting light. Example : Moon, Table , Chair ,etc.
  4. 4.  Light rays is a line of light. Light travel in all direction. Line of light can be seen clearly if they travel in one direction.
  5. 5.  Transparent let light to pass on. Ex: Glass , windows. Translucent not let pass some light but pass some light through them. Ex : Tracing Paper Opaque not let all light to pass through them. Ex: wood, metal.
  6. 6.  As light cannot pass through opaque object it will make a dark area usually behind the object it was called shadows. Te size of the shadows depends on the light source and the distance of the light source and the object.
  7. 7.  The greater the light source there will be a shadow that have dark in the middle and grey surround it. The less the light source the darker the shadow in the middle part.
  8. 8.  The further the distance between the object and the light source will make small shadow. The shorter the distance between object and light source it will make a big shadow.
  9. 9.  You can see object because the object is reflecting the light and the reflected light will be caught by our eye.
  10. 10.  Incident ray is a light that strike the surface of something. Reflected ray is a light ray that is reflected from a surface Normal is a line that is perpendicular at 90 degree to the surface where a ray strike. Angle of incidence is the angle between incident ray and normal.
  11. 11.  Angle of reflection is the angle between reflection ray and the normal line. Plane mirror is a mirror with flat surface. Image is appearance of an object in smooth shiny surface.
  12. 12.  When light ray strike a smooth surface the angle of reflection is equal to the angle of incidence. When reflected light reach your eyes you will be able to see the image.
  13. 13.  Real image Virtual image
  14. 14.  Real image is a image that cannot be projected into flat surface. Virtual image is a image you see in a mirror that are in the same size but only in opposite directions.
  15. 15.  Light rays that strike the rough surface will not have same angle of incidence and angle of reflection. Because of this effect you will not able to see your image in the rough surface thing.
  16. 16.  Refraction is light that is bend because of different position of object and different medium. The angle which the ray makes with normal is called angle of refraction.
  17. 17.  Light travel in different speeds in different media. If the light slows down it bends toward the normal. A light ray can appear different direction than the actual place example stone in water.
  18. 18.  Periscope is an equipment made by two plane mirror
  19. 19.  If the sun light strikes the prism in certain angle and stop by a white screen it will make a range of color is spread out and called as spectrum. The sun light contains different color because have different wave length and travel in different speed.
  20. 20.  Rainbow are appear because of the refraction and reflection of the sun light by the water droplets. There can be two rainbow if there is 2 reflection occur.
  21. 21.  Absorbing color Reflecting color
  22. 22.  If all the colors are reflected the color will seem to have white color If all colors are absorb the color of the object will seem black. Usually object absorb some color and reflected other colors.
  23. 23.  Because some object reflecting and absorb some color so if you put blue glass the only color that can be pass through is blue and the other reflected.
  24. 24.  When different type of light color is mix up it can make new color. Ex blue and red become magenta. When three beams of light is shining into white screen it will produce 3 secondary color and white color.

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