Light is a form of electromagnetic radiation that travels in straight lines. Objects that emit their own light, like the sun and stars, are called luminous objects. Objects that do not emit light, like the moon, can only be seen when light from luminous objects reflects off of their surfaces. Light interacts with materials in different ways depending on whether the material is transparent, translucent, or opaque. Shadows form in areas without light and can be cast by objects that block light sources like the sun or moon. The reflection, refraction, and dispersion of light are important optical phenomena that allow for vision and the formation of rainbows, colors, and images.

1. By: Pawitra, G.7

2. Light is a form of energy. It is a form of
electromagnetic radiation.

3. Is objects that emit light.
Release light together with a large amount
of heat.
Examples : Sun, stars, fire and candle flames.

4. Is objects that do not emit light.
Can only be seen if they are reflecting light from a
luminous source.
The moon is a non-luminous body because the moon
get light from sunlight that is reflected.

5. Light leaves the surface of a luminous object in all
directions but if some of the light is made to pass
through a hole it can be seen to travel in straight
lines.
Ray is smaller lines of light.

6. Can be classified as transparent, translucent and
opaque.

7. TRANSPARENT MATERIAL
When light shines on a transparent material it
passes through it, so objects on the other side
of it can be seen clearly.

8. o When light shines on a translucent material some of the
light passes through but many light rays are scattered.

9. Opaque material
When light shines on an opaque material none of
the light passes through it.

10. Shadow
Is a region without light, forms behind the object.
Shadows are also cast by the Moon and the Earth.

11. Reflecting light
The way light is reflected from a surface depends on
whether the surface is smooth or rough

12. Reflections
Incident ray – a light ray that strikes a surface
Reflected ray – a light ray that is reflected from a
surface
Normal – a line perpendicular to the surface where
the incident ray strikes.
Angle of incidence – the angle between the incident
ray and the normal
Angle of reflection – the angle between the reflected
ray and the normal
Plane mirror – a mirror with a flat surface
Image – the appearance of an object in a
smooth, shiny surface

13. Objects with smooth surface
Light rays are reflected from a smooth surface at the same
angle at which they strike it

14. Two kinds of images
They are real image and virtual image.

15. Real image
Can be formed on a screen.
Example: produced on a cinema screen by biconvex
lenses.

16. Virtual image
Can’t be projected onto a surface but only appear
to exist.
Example: in a plane mirror or other smooth, shiny
surface.

17. The periscope
Is an instrument for observation from a concealed
position.

18. Objects with rough surfaces
When light rays strike any objects with rough
surfaces the rays are scattered in different
directions.
Objects that have a rough surfaces : woollen
pullover and paper.

19. Passing light through transparent
materials
A ray of light is shone on the side of a glass block
and the ray passes straight through.
If the glass block is tilted the ray of light follows the
path.

20. Refraction
Is the bending of the light ray
The angle that the refracted ray makes with the
normal is called the angle of refraction.

21. The prism
White light passing through a prism is split up into
its constituent colour, forming spectrum.

22. The rainbow
Weaker rainbow is seen above the first because 2
reflections occur in each droplet.
In the second rainbow the order of colours is
reversed.

23. Colour
Is the visual perceptual property corresponding in
humans to the categories called red, green, blue
and others.

24. When a ray of sunlight strikes the surface of an
object, all different colours in it may be reflected or
they may all be absorbed.
All colours that are reflected the object appears
white.
All colours that are absorbed the object appears
black.

25. Filtering colours
Sheets of coloured plastic or glass can filter the
colours in light.
Example : a blue filter allows only blue light to pass
through.

26. Combining colours
Red, green and blue are called the primary colours
of light.

27. Colours and paint
3 different colours of paint, ink or dye can be used
to make almost all the other colours.
These 3 colours are yellow, magenta and cyan.
Tiny dots of the 3 colours form the printed picture.

28. THANK YOU FOR
YOUR ATTENTION…