1. Light and Sight

2. 1.Source of light
• Luminous object: object that give out light as
the result of the excited atoms receive energy.
• Non luminous object: Object that not send out
light.
• Laser: A type of light source in which their
excited atoms act together and emit a narrow
light.

3. 2.Rays and beams
• Rays travel in straight lines
• The path in which light pass= rays
• A beam is a stream of light.
• Beam of light can be parallel, converging,
diverging.

4. 3.Shadows
• Opaque: Object that doesn’t let light pass
• Small source of light give sharp shadows with
dark color all over.
• Large large amount of light give a shadows
with a pitch dark on the centre with gray area
surrounds it.
• Umbra: Dark region
• Penumbra: Gray area

5. 4.Speed of Light
• Very fast
• Faster than sound

6. 5.Law of reflection
• Normal : an imaginary line that perpendicular
90 degree to the surface.
• Law of reflection : The angle of incidence
equals angle of reflection.

7. 6.Periscope
• Instrument that use 2 mirrors.

8. 7.Regular and diffuse reflection
• Regular reflection is on a smooth surface.
• Diffuse reflection is on rough surface.
• Diffuse reflection does not follow law of
reflection.

9. 8. Real image and Virtual image
• Real image is the image that can be from on
screen and produced by light rays that passed
through it.
• Virtual image is the image that cannot be
produced on screen and produced by rays that
seemed to pass through it but not.

10. 9. Lateral inversion
• This is an effect produced by plane mirror.
• Your left and right eyes are interchanged.
• Occurs whenever an image is formed by one
reflection.

11. 10. Properties of plane mirror
• As far behind the mirror as the object is in
front and the line joining the object and image
is perpendicular to the mirror.
• The same size as the object.
• Virtual
• Laterally inverted

12. 11. Kaleidoscope
• A set of two mirror set at an angle to produce
multiple image.
• Formula to find the image produce by two
mirrors forming specific angle:
360
X
- 1

13. 12. Facts about reflection
• Light ray that enter a denser medium have angle
of reflection smaller than angle of incidence.
• A light ray is bent away from the normal when
enter a less dense medium.
• A light ray is bent towards the normal if it enters
a denser medium.
• A ray emerging from parallel sided block is
parallel from ray that enter the block.
• A ray enter at the normal of an object is not
refracted.

14. 13. Refraction index
• Refraction happens because change of speed
of light.
• Reactive index =
Speed of light in air or 1st medium
Speed of light in 2nd medium

15. 14.dispersion
• The spread out of color spectrum when white
color light pass through a prism.

16. 15.Critical angle
• The angle at which the angle of refraction is
90 degree.
• When the light does not pass the boundary it
is said that it undergo total internal reflection.

17. 16.Multiple images
• It happened because of the multiple reflection
inside a glass of mirror which cause blurring.

18. 17.Total reflecting prisms
• The prism which completely reflecting light
rays.