Light and matter

How does light interact with matter?

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A Light Source emits (gives off) electromagnetic radiation

• sun

• light bulb

• fire

• bioluminescence

How does light move from a source to your eye?

• Light travels as waves moving away from a source

• Light can travel directly from a source

• Light can also reflect off some objects

Multiple Select

Click on ALL the objects that are light sources

When light hits different surfaces it will be

• Transmitted: to pass along or go through

• Absorbed: to take in, to suck up and NOT reflect

• Reflected: to bounce back and not pass through

• OR some combination of the three

Multiple Select

When light strikes different surfaces, it can be... (choose ALL that apply)

• reflected

• absorbed

• transmitted

• ignored

Transmission:

Transparent vs Translucent

•  A material that allows most or all of the light striking it to pass through, and through which objects can be seen clearly is transparent.

• A material that allows some of the light that strikes it to pass through, but through which objects appear blurry is translucent

Absorption: Some materials absorb most of the light that strikes them. These materials transmit no light.

• A material through which light does not pass is opaque

Multiple Choice

A surface which allows most or all light to pass through is

• transparent

• translucent

• opaque

Multiple Choice

A sweatshirt is an example of a surface which is

• transparent

• translucent

• opaque

What is reflection?

When light strikes a surface and some or all of it bounces off. What you see when you look at an object depends on how its surface reflects light

Law of reflection

Law of reflection states that when a ray of light reflects off a surface, the angle of incidence (incoming light ray)  is equal to the angle of reflection (reflected light ray)

Regular reflection

occurs when parallel rays of light hit a smooth surface and are reflected in a predictable way, creating a reflected image.

Examples: mirror, shiny metal, glass

Irregular (diffuse) reflection

occurs when parallel rays of light hit a bumpy, irregular surface and are reflected at different angles, creating NO reflected image.

Examples: wall, t-shirt, book

Multiple Choice

When light waves bounce off surfaces that they can't pass through they are

• tranparented

• transmitted

• reflected

Multiple Select

Choose all examples of objects that show regular reflection.

Multiple Select

Chose all examples of objects that show irregular (diffuse) reflection.

Images in a plane (flat) mirror

An image forms when light bounces off an object to a reflecting surface. The surface reflects the light back to your eye. Your brain knows that light travels in straight lines, so it perceives this light as an image of the object. Your brain identifies where the light rays appear to come from, not their actual paths.

Virtual image

• an image that forms from light rays that diverge, or change direction

• is the same size as the object

• no object is actually located at the place where the image appears

Multiple Choice

There is a real object at the position where the image appears to be in a plane mirror.

• true

• false