Physics-- Lenses

List the three rays useful for the construction of a ray diagram

1. A ray parallel to the principal axis that passes through the focal point after refraction by the lens. 2. a rays through the center of the lens that does not change direction. 3. a ray through the focal point in front of the lens that emerges parallel to the principal axis after refraction by the lens.

Compound Microscope

A compound microscope uses two converging lenses of short focal lenth. the first lens is called the objective lens

CONVERGING LENS IN SUMMARIZATION

A converging lens is a simple magnifying glass when the object is within one focal length of the lens. The image is then virtual, magnified, and right-side up. When the object is beyond one focal length, a converging lens produces a real, inverted image. The location of the image depends on how close the object is to the focal point. If it is close to the focal point, the image is far away (as with slide projectors and movie projectors). If the object is far from the focal point, the image is nearer (as with a camera). In all cases where a real image is formed, the object and the image are on opposite sides of the lens.

Ray Diagrams

A diagram showing rays that can be drawn to determine the size and location of an image formed by a mirror or lens

How does a lens affect light coming from the left compared to the right?

A lens affects light coming from the right in the same ways as light coming from the left; therefore, a lens has two focal points and two focal planes.

Focal Plane

A plane passing through either focal point of a lens that is perpendicular to the principal axis. For a converging lens, any incident parallel beam of light converges to a point somewhere on a focal plane. For a diverging lens, such a beam appears to come from a point on a focal plane

Telescope

A simple telescope uses a lens to form a real image of a distant object. The real image is not caught on film but is projected in space to be examined by another lens used as a magnifying glass.

Explain what happens to the angle of view when you are closer to an object, compared to farther away

An object far away is seen through a relatively small angle of view. When you are closer, the same object is seen through a larger angle of view. This wider angle enables the perception of more detail

DRAW A DIAGRAM OF THE KEY FEATURES OF A CONVERGING LENS

DRAW, LUKE

Focal Point

For a converging lens, the point at which a beam of light parallel to the principal axis converges. For a diverging lens, the point from which such a beam appears to come.

objective lens

In an optical device using compound lenses, the lens closest to the object observed

Converging Lens

Lens that is thicker in the middle and rays of light that are initially parallel are made to converge.

Principal Axis

Line joining the centers of curvature of its surfaces of a lens

aberrations

MOst cameras make use of compound lenses to minimize distortions called aberrations

When does magnification occur

Magnification occurs when an image is observed through a wider angle with the use of a lens than without the lens and allows more detail to be seen. A magnifying glass is simply a converging lens that increased the angle of view and allows more detail to be seen

Camera

The camera consists of a lens and sensitive film mounted in a lighttight box. The lens froms a real, inverted image on the film aberrations

Focal Length

The distance between the center of a lens and either focal point

What do the moving patterns of bright lines on the bottom of swimming pools result from?

The moving patterns of bright lines on the bottom of a swimming pool results from the uneven surfaces of water, which behaves as a moving blanket of lenses

Diverging Lens

Thinner in the middle and the rays of light are made to diverge

To construct a ray diagram what must be known?

To construct a ray diagram, the size and location of the object, its distance from the center of the lens, and the focal length of the lens must be known.

List some lenses

Today, lenses are used in many optical instruments. Among these are the camera, telescope (and binoculars), compound microscope, and projector

What happens when a diverging lens is used alone, etc.

When a diverging lens is used alone, the image is ALWAYS virtual, right-side up, and small than the object. When you look at an object to be photographed through the viewfiner, you see a right-side up virtual image that approximates the same proportions as the photograph to be taken

Lens

When a piece of glass has just the right shape, it bends parallel rays of light so that they cross and form an image.

Explain the relationship between the focal length and lens when the lens is thin and not

When the lens is thin, the focal lengths on either side are equal, even when the curvatures on the two sides are not

Explains what happens when the lens of a camera is set for distant objects

When the lens of a camera is set for distant objects, the film is in the focal plane behind the lens in the camera.

DIVERGING LENS IN SUMMARIZATION

When the object is viewed with a diverging lens, the image is virtual, reduced, and right-side up. This is true for all locations of the object. In all cases where a virtual image is formed, the object and the image are on the same side of the lens.

Explain what you do to use a magnifying glass

When you use a magnifying glass, you hold it close to the object you wish to see magnified. This is because a converging lens will magnify only when the object is between the focal point and the lens. The magnified image will be father from the lens than the object, and it will be right side up.

the projector

a concave mirror reflects light from an intense source back onto a pair of condenser lenses. The condenser lenses direct light through the slide or movie frame to a projection lens.

accommodation

adjustments in focusing of the image on the retina are made by changing the thickness and sahpe of the lens to regulate its focal lenth

Real image

an image that is formed by converging light rays and that can be displayed on a screen

achromatic lenses

combine simple lenses of different kinds of glass

Astigmatism

defect that results when the cornea is curved more in one direction than the other

aberrations

distortions in an image

what are the differences between farsighted people, normal, and nearsighted people

if you have normal vision, your eye can clearly see objects from infinity down to 25cm. the eyes of a farsighted person form images BEHIND the retina. the eyeball is too short. they can't focus on objects near.the remedy is wearing converging lenses. a nearsighted person can see nearby objects clearly, but cannot see distant objects clearly because they are focused too near the lens, the eyeabll is too long. a remedy is to wear diverging lenses

eyepiece

lens of telescope closest to the eye; enlarges the real image formed by the first lens

Terrestrial telescope

produces image right-side up. these are in binoculars

spherical aberration

results when light passwes thorugh the edges of a lens and focuses at a slightly different place from light passsing through the center of the lens

fovea

small region in the center of our field of view where we have the most distinct vision. much greater detail can be seen here than at the side parts of the eye

blind spot

spot in the retina where the nerves carrying all the information leave the eye in a narrow bundle

ciliary muscle

surrounds lens and controls accommodation

refracting telescopes

telescopes that use lenses are frefracting telescopes. Larger stronomical telescopes use mirrors instead of lenses

the eye

the eye is similar to camera. the amount of light that enters is regulated by the iris. light enters through the transparent covering called the cornear, light passes through tht epupil and lens and is focued on a layer of tissue at the back on the eye- the retina- extremely sensitive to light.

astronomical telescope

the image is inverted, which explains why maps of the moon are printed with the moon upside down

what's the main difference between a camera and the eye

the principal difference between a camera and the human eye has to do with focusing. In a camera, focusing is accomplsihed by altering the distance between the lens and the film. IN the human eye, most of the focusing is done by the cornea, the transparent membrane at the outside of the eye.

chromatic aberration

the result of the different speeds of light of various colors and hence the different refractions they undergo.