Light presentation

LIGHTLIGHT

Made by –TUSHAR GOYAL

LightLight

In this unit:

1) Properties of light2) Mirrors3) Colors

1 – Properties of Light1 – Properties of Light

Light travels in straight lines:

Laser

Light travels VERY FAST – around 300,000 kilometres per second.

At this speed it can go around the world 8 times in one second.

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.

We see things because they reflect light into our eyes:

Homework

Shadows

Shadows are places where light is “blocked”:

Rays of light

Properties of Light Properties of Light summarysummary

1) Light travels in straight lines2) Light travels much faster than sound3) We see things because they reflect

light into our eyes4) Shadows are formed when light is

blocked by an object

ReflectionReflectionReal Image – Real Image –

–Real image is formed when reflected rays of light actually meet at a point.

–Always inverted.–It is formed on the screen.

ReflectionReflection

Virtual Image– Virtual Image–

–“Not Real” because it cannot be projected

–Image only seems to be there!

Virtual Images in Plane Virtual Images in Plane MirrorsMirrors

If light energy doesn't flow from the image, the image is "virtual".

Rays seem to come from behindthe mirror, but, of course, theydon't.  It is virtually as if the rayswere coming from behind the mirror.

"Virtually":  the same as if

As far as the eye-brain system isconcerned, the effect is the sameas would occur if the mirror wereabsent and the chess piece were actually located at the spot labeled "virtual image".

Plane MirrorPlane Mirror

“image” you

“real” you

•Useful to think in terms of Useful to think in terms of imagesimages

LEFT- RIGHT REVERSALLEFT- RIGHT REVERSAL

Spherical Mirrors

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

Convex MirrorsConvex Mirrors

•Curves outward•Reduces images•Virtual images

–Use: Rear view mirrors etc.

CAUTION! Objects are closer than they appear!

Convex Convex LensesLenses

Thicker in the center than Thicker in the center than edges. edges.

– Lens that converges (brings together) light rays.

– Forms real images and virtual images depending on position of the object

The Magnifier

Concave Concave LensesLenses

Lenses that are Lenses that are thicker at the edges thicker at the edges and thinner in the and thinner in the center. center.

– Diverges light rays

– All images areerect and reduced.

The De-Magnifier

ColourColour

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.

The colours of the rainbow:The colours of the rainbow:

RedOrangeYellowGreenBlue

IndigoViolet

Adding coloursAdding coloursWhite 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 makes magenta (purple)

Adding blue and green makes cyan

(light blue)

Adding all three makes white again

Adding red and green makes yellow

Seeing colourSeeing colourThe colour an object appears depends on the

colours of light it reflects.

For example, a red book only reflects red light:

White

light

Only red light is

reflected

A white hat would reflect all seven colours:

A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and

blue):

Purple light

White

light

Thank YouThank You