Reflection and Refraction of Light

Reflection of Light

• Every object absorbs some light and reflects some light

• Why is the sun different?– The sun makes its own light– The light that comes from your table to your eyes

is from the sun or a lamp and then reflects to your eyes

• How can we trace light?– Ray diagrams are used to trace the path of light

Ray Diagrams

How does light reflect?• Light reflects at an angle• Rough surfaces - light that strikes the surface will be

reflected at all angles– Called DIFFUSE REFLECTION

• Smooth surfaces – light that strikes a smooth surface like a mirror will all reflect in a single direction

How do you see something?

• Light from the sun appears white, however when shone through a prism, it will separate into various colors (visible spectrum of electromag. waves)

• Objects have color because they reflect certain wavelengths of light

Why does a plant appear to be green?

• It absorbs the other wavelengths and reflects the green light (550 nm)

• Light really is not “green” – your brain interprets light at certain wavelengths as certain colors

• Petals of a red rose look red because they absorb wavelengths and then reflect the red light

Black is not a color – it is the absence of color

Refraction of Light• What happens to light

waves when they travel?

• Through empty space – travel in straight line

• Refraction – how light bends when passing from one medium to another

• Light changes direction because the speed of light is different in different mediums

How is light refracted?When light goes from traveling fast to a medium

where it is traveling more slowly, the ray will be bent toward the normal• Like one wheel of a lawnmower hitting the grass• Like a car wheel going into the sand

When light goes from traveling slower to a medium when it is traveling faster, the ray is bent away from the normal

How do objects appear if light is refracted?

• Objects appear to be in a different position

• The path of the light is changed as it goes from one medium to another

• However the brain still sees it as though the light traveled in a straight line

• So, the position of the object (cat of fish) looks different than where it really is

Diffraction • Diffraction is the BENDING of waves around an

edge.– Ex- Hearing sound waves from around a corner– When waves pass the edge of an object or pass

through an OPENING, they spread out as if a new wave were created there.

– Diffraction is the reason a SHADOW never has perfectly sharp edges.