Refraction and Lenses

Refraction and Lenses

What Happens When Light Hits an Object?

What Determines the Type of Image Formed by a Lens?

What happens when light hits an object?

• Reflection

• Refraction

• Absorption

Reflection

• Occurs when light bounces off of an object

• Regular & Diffuse Reflections

• The colors we perceive are those that are reflected off of an object.

Refraction

• the bending of light as it changes speed

• some mediums cause light to bend more than others

• index of refraction: a measure of how much a light ray bends when it enters a specific medium

Index of Refraction

• 1 on the index is equal to no bending at all....light travels straight through a vacuum.

• The higher the index of refraction the more the light bends

Absorption

• light waves are absorbed by an object

• We only see the colors that are NOT absorbed by that object.

Multiple Choice

What are three things that can happen when light hits an object?

• Regular, Diffuse, Obtuse

• Reflection, Refraction, and Absorption

• Concave, Convex, Plane

Multiple Choice

Which word best describes what happens to light when it "refracts"?

• stops

• bends

Multiple Choice

We do not see the colors that are absorbed, only those that are reflected off of an object.

• True

• False

Multiple Select

What do we call the scale used to identify how much light slows down and bends when entering different materials?

• Index of Refraction

• Scale of Bending

Lenses

• A lens is a curved piece of glass (or other transparent material) that refracts light

Types of lenses

• Concave Lens

• Convex Lens

Concave Lens

• "caves in" on either side of lens

• thinner in the middle than at the edges

• The parallel light rays enter and then exit angled away from one another never meeting at a focal point

• Like a Convex Mirror it produces only virtual images

Convex Lens

• Thicker in the center than the edges

• As parallel light rays enter the lens they exit at an angle so they meet at a focal point

• If the object is between the focal point and the lens then a virtual image is produced

• If the object is beyond the focal point then a real image is produced.

Multiple Choice

Which type of lens is thicker in the middle?

• Concave

• Convex

Multiple Choice

Which type of lens in thinner in the middle and thicker on the edges

• Concave

• Convex

Multiple Choice

What type of lens do we have in our eye?

• Concave

• Convex

Near Sighted or Far Sighted?

• Near Sighted (Myopia) This makes the affected people see nearby objects clearly, but distant objects in a blurry manner

• The contact lens used for this condition is a concave or diverging lens that raises the focal length of the light entering the eye.

• Far Sighted (Hyperopia) A person cannot see things close up but may be able to see distances more easily.

• The contact lens that is convex or converging in nature is used to correct this condition.

The Human Eye

• Retina: thin layer of cells that line the back of the eye

• Lens: convex shape, bends light to form an image on the retina

• pupil: the muscle that contracts when exposed to sunlight

• Iris: the color part of the eye

• Cornea: the protective outer layer

Multiple Choice

What do we call the back of the eye where images are projected as light?

• pupil

• retina

• iris

• cornea

Multiple Choice

What is the part of the eye that bends light so that an image can be projected onto the retina?

• optic nerve

• lens

• pupil

Multiple Choice

What do we call the muscle in the eye that contracts in sunlight?

• retina

• lens

• pupil

Multiple Choice

What do you call the color part of the eye?

• retina

• optic nerve

• iris

• pupil

Multiple Choice

What is the protective layer on the outer eye called?

• Cornea

• lens

• pupil