Science of Light

LightBy Khan Imran

Hey friends, do you see the light? Why? How?

What Is Light? In this PowerPoint presentation:

1) Properties of light2) Colours3) Reflection - Mirrors4) Refraction - Lenses

Properties of Light

Light travels in straight lines:

Laser

2.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.

3.Light travels VERY FAST – about 300,000 kilometres per second or 186,000

miles per second.

At this speed light could travel the equivalent of 8 times around the world in one second!

4.Light can create shadows

Shadows are places where light is “blocked”:

Rays of light

We see things because they reflect light into our eyes!

This is literally the only way we get to see things! ALL

objects we see either create light or reflect light!!

Homework

Light is a form of energy called Electromagnetic Radiation.

Electromagnetic Radiation comes from the sun and other sources

Properties of Light summary1) Light travels in straight lines and is a form

of energy2) Light travels much faster (a million times

faster!) than sound3) We see things because they reflect light

into our eyes4) Shadows are formed when light is blocked

by an object5) Visible light is only a small part of the

electromagnetic spectrum; the other parts are invisible to the human eye but not necessarily the eyes of other animals.

Part 2 - Reflection and Mirrors

Regular vs. Diffuse Reflection

Smooth, shiny surfaces have a regular reflection:

Rough, dull surfaces have a diffuse reflection.

Diffuse reflection is when light is scattered in different directions

Review of Reflection1. Two types of reflection, regular and diffuse

2. Mirrors come in 3 types: plane, convex and concave. Each has a distinct shape and use.

3. Mirrors can make virtual images or real images depending on their type

4. Virtual images - light rays do not meet and the image is always upright or right-side-up

5. Real images - always upside down and are formed when light rays actually meet

Using mirrorsTwo examples:

1) A periscope

2) A car headlight

Types of Mirrors: Plane, Concave, Convex

Plane mirrors are flat and make “virtual images”. The images is “virtual” because the light rays do not come from the image, they only appear to

Concave Mirrors are curved inward - just remember, you go “in” to a cave, and “in” to a concave mirror!

Convex mirrors are mirrors that curve outward

Convex mirrors are used for security purposes, in cars etc. They allow us to see a wide view. The images they make are virtual

Refraction• Refraction is when waves speed up or slow down due to travelling in a different medium

• A medium is something that light waves will travel through

• Light rays are slowed down by the water

• Causes the ruler to look bent at the surface

• The mediums in this example are water and air .

The degree that light bends when it enters a new medium is called the “index of refraction”

Light hitting at anangle is bent

Light hitting straight on is not bent

Review of Refraction1. Light rays slow down when they

enter a new medium

2. Refraction can cause light rays to change their direction

3. All transparent materials have their own “index of refraction”

4. Light is refracted when it passes through lenses and this creates images

ColorPart 3 - Color In this section of the

PowerPoint you will learn about color and how we can mix colors to create other colors. We will also learn how light helps us to see various colors around us.

ColourWhite 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:

RedOrangeYellowGreenBlue

IndigoViolet

Just remember ROY G. BIV

Adding colours of lightWhite 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 colourThe colour an object appears depends on

the colours of light it reflects.

For example, a red book only reflects red light:

White

lightOnly 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