How does light travel and

interact with matter?

Chapter 12: Lesson 3:

Distance traveled by light from sun to earth

=90 million miles

What is light made up of?

Electric waves Magnetic waves

Light can travel through vacuum.

Speed of light in vacuum is faster than its speed in solid, liquid or gas.

Distance between one peak and the next in a wave.

To calculate the speed of a wave:

Speed = Wavelength x frequency

Types of materials

TransparentTranslucent

Opaque

Allow most light to pass through them. Allow some light to

pass through them.

No light can pass through them.

Determine what is transparent, translucent and opaque.

When light does not pass through opaque objects it forms SHADOWS.

Position of the SHADOW depends upon the position of the light source.

Example:

Draw the sunlight rays falling on the objects.

Determine the

position of the sun in

the following pictures.

To change the size of the shadow, move closer or away from the light

source.

How do we see objects?

Light hits the objects and scatters (we see objects).

Law of reflection:Angle of incoming light = angle of

reflected light

How can we see images in mirrors?

Draw the

light rays that

helps the girl see her image.

The image in a mirror is clear because most of the light is reflected off the

mirror’s smooth surface.

Look at the spoon in the glass of water.

Is the spoon broken?

The spoon is not broken.

When light enters a different medium it bends and when it is leaving it bends to

the opposite side again.

Bending of light while passing from on

substance to another is called

REFRACTION.

Draw the light rays to explain what is happening.

WaterAir Air

Draw the light rays to explain what is Refraction.

Sunlight is white light,

when it passes

through a rain drop it is divided

into 7 colors.

When white light passes through a prism it comes out as a spectrum (7 colors of

rainbow)

The colors of the spectrum.

Each color has a different wavelength.

Red light has long wavelength.

Violet light has Short wavelength.

The way we see colored objects depends on the color that is reflected.

Example:

The leaf is green so it absorbs all light and green light is reflected.

The apple is red so it absorbs all light and red light is reflected.

Predict what light is reflected for you to see the color.