PHYSICS
CONTENT WORK- Demonstration / Name:Ashley Guenter
Period:6
Date: May 22, 2008
Overview of Major Concept(s)
State and Explain Major Concept(s)::
" A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, concentrating or diverging the beam. A simple lens is a lens consisting of a single optical element. A compound lens is an array of simple lenses (elements) with a common axis; the use of multiple elements allows more optical aberrations to be corrected than is possible with a single element. Manufactured lenses are typically made of glass or transparent plastic. Elements which refract electromagnetic radiation outside the visual spectrum are also called lenses: for instance, a microwave lens can be made from paraffin wax."
Historical Perspective:
Benjiman Franklin created the first bi focals.
George washington wore the first pair of glasses ever made with wood and plastic wrap.
Application of Concept(s):
You can apply these concepts when using a camera, to better understand how they work and also know the best distance to stand when trying to focus on a certain object.
Also if you can't see you can get some glasses for the right condition that you might have so you can correct your vision properly.
Think and Explain Questions
Answers:
2. The main test is that a real image exists in space and can be see on a screen or ground glass in the light path. The eye can also see a real image if it is in the light from the lens, but only a part of the image can be seen. (The field is limited by the aperture of the lens.)
Only the eye (or another optical device) can see a virtual image, which does not actually exist, but only appears to exist since the light rays behave as if they came from an object.
3. Because magnifying glasses with strong power or small focal lengths can concentrate enough sun rays on the focal point to ignite a fire in a combustible substance like cotton, paper, wood etc.
Magnifying glass is basically a convex lens. When parallel lines fall on a magnifying glass the are converged and meet on a single point (i.e. focal point) on the other side of the glass (lens). If these are sun rays, a strong magnifying glass can concentrate enough sun rays to "burn" a combustible substance kept at the point of convergence (i.e. focal point)
This is the reason it is offer referred to as "burning glass"
4. A camera consists of a lens and sensitive film mounted in a light tight box. In many cameras, the lens is mounted in a screw mount witch can be moved to or from to adjust the distance between the lens and the film. The lens forms a real introverted image on the film.
5. No, because your eye will not allow you to do so.
6. Both
7. The real image is not caught on film but is projected in space to be examined by another lens used as a magnifying glass. The second lens called the eye piece is positioned so that the image produced by the first lens within one focal length.
8. It is because the projector inverts and reverses the image ... so you put the slides in upside down and backwards.
9. Because of the camera film.
10. A concave mirror reflects light from an intense source back onto a pair of condenser lenses. These direct the light through the slide or movie frame to a projection lens. The projected lens is mounted in a sliding tube so that It can positioned to or from the focus as a sharp image on the screen.
11. Presbyopia is the common condition where the eye become less able to focus on close objects over time in older people. Presbyopia is well known. The word itself is Greek for "old person". The exact cause is not known. Loss of elasticity in the eye lens is only one theory. Loss of muscle strength around the eye lens is another.
12. I guess not because it is the lens in the telescope that causes the light to bend, therefore focussing on the object that is far away or small. if light moved the same speed in the glass, the light would not bend and it wouldnt work..
Review Questions
Answers:
1. Converging lens is thicker in the middle and converges parallel rays of light. A diverging lens is thinner in the middle and deverges parallel rays of light.
2. In aconverging lens a focal point is the point at which a beam of light parallel to the principal axis converges and the focal plane is a plane that passes through either a focal point of a lens perpendicular to the principal axis.
3. A virtual image is formed through reflection or refraction that can be seen by an observer but cannot e projected and a real image is formed by converging light rays that can be displayed on a screen.
4.The three rays are:
1. A ray parallel to the principal axis which passes through the focal point after refraction by the lens.
2. A ray through the center of the lens which does not change direction.
3. A ray through the focal point in front of the lens which emerges parallel to the principal axis after refraction by the lens.
5. Any two rays
6. It applies to both
7. Because there are two lenses and the second lens called the eyepiece, forms an enlarged eirtual image of the real image.
8. The astronomical telescope has two lenses and a terestrial telescope has three.
9. A compound microscope enlarges an already enlarged image and a telescope does not.
10. A camera
11. Because there is a spot in your retina where the nerves carrying all the info run out.
12. When your farsighted the persons eye ball is too short and they see better far away. When your nearsighted the persons eye ball is too long and they have a hard time seeing far away.
13.It is an eye defect that results when the cornea is curved more in one direction this can be corrected by cylindrical corrective lenses that have more curvature in one direction than other.
14. Spherical aberration results when light passes through the edges of a lens and focuses at a slightly different place from tlight passing through the center of the lens, and is corrected in good optical instruments by a combination of lenses. A chromatic aberration is the result of the different speeds of various colors and hense the different refractions they undergo. This can be correced with achromatic lenses.