1) Light travels in straight lines at extremely high speeds of around 300,000 km/s. 2) We see objects because they reflect light into our eyes, and shadows are formed when light is blocked. 3) Mirrors form real or virtual images depending on whether the reflected rays of light actually meet at a point, with virtual images appearing as if they exist but not being projectable.

1. LIGHT
Made by –
TUSHAR GOYAL

2. Light
In this unit:
1) Properties of light
2) Mirrors
3) Colors

3. 1 – Properties of Light
Light travels in straight lines:
Laser

4. Light travels VERY FAST – around
300,000 kilometres per second.
At this speed it can
go around the world 8
times in one second.

5. Light travels much faster than sound. For example:
1) Thunder and lightning
start at the same time,
but we will see the
lightning first.
2) When a starting pistol
is fired we see the
smoke first and then
hear the bang.

6. We see things because they
reflect light into our eyes:
Homework

7. Shadows
Shadows are places where light is “blocked”:
Rays of light

8. Properties of Light summary
1) Light travels in straight lines
2) Light travels much faster than sound
3) We see things because they reflect light
into our eyes
4) Shadows are formed when light is blocked
by an object

9. Reflection
Real Image –
– Real image is formed when
reflected rays of light actually
meet at a point.
– Always inverted.
– It is formed on the screen.

10. Reflection
Virtual Image–
– “Not Real” because it cannot
be projected
– Image only seems to be there!

11. Virtual Images in Plane
Mirrors
Rays seem to come from behind
the mirror, but, of course, they
don't. It is virtually as if the rays
were coming from behind the
mirror.
"Virtually": the same as if
As far as the eye-brain system is
concerned, the effect is the same
as would occur if the mirror were
absent and the chess piece were actually
located at the spot labeled "virtual
If light energy doesn't flow from the
image".
image, the image is "virtual".

12. Plane Mirror
•Useful to think in terms of images
“real” you
“image” you

13. LEFT- RIGHT REVERSAL

14. Spherical Mirrors
Spherical mirrors have a central axis (a radius of
the sphere) and a center of curvature (the center
of the sphere).

15. Convex Mirrors
• Curves outward
• Reduces images
• Virtual images
–Use: Rear view mirrors
etc.
CAUTION! Objects are closer than
they appear!

16. Convex Lenses
Thicker in the center
than edges.
– Lens that
converges (brings
together) light The Magnifier
rays.
– Forms real images
and virtual images
depending on
position of the
object

17. Concave Lenses
Lenses that are
thicker at the edges
and thinner in the
center.
– Diverges light The De-Magnifier
rays
– All images are
erect and
reduced.

18. Colour
White light is not a single colour; it is made
up of a mixture of the seven colours of the
rainbow.
We can demonstrate this by
splitting white light with a
prism:
This is how rainbows are
formed: sunlight is “split up”
by raindrops.

19. The colours of the rainbow:
Red
Orange
Yellow
Green
Blue
Indigo
Violet

20. Adding colours
White light can be split up to make separate colours.
These colours can be added together again.
The primary colours of light are red, blue and green:
Adding blue and red Adding blue and
makes magenta green makes cyan
(purple) (light blue)
Adding red Adding all
and green three makes
makes yellow white again

21. Seeing colour
The colour an object appears depends on the colours
of light it reflects.
For example, a red book only reflects red light:
White Only red light
light is reflected

22. A pair of purple trousers would reflect purple light
(and red and blue, as purple is made up of red and blue):
Purple light
A white hat would reflect all seven colours:
White
light

23. Thank You