physics 222, module 8

ray tracing

the technique of determining or following (tracing) the paths that light rays take in order to determine the position and size of an image

absorptive or reflective character

the true color of an object is defined by...

more info needed to calculate MP

Suppose that a microscope has an objective whose focal length is 1.00 mm and an eyepiece whose focal length is 25.0 mm. What is the magnifying power (M)) of the microscope?

the distance at which parallel light rays are focused

The focal length of a converging lens is

correction

The geometry of a cylindrical (or toric) lens focuses light differently across different planes, compensating for this uneven focus of the eye

near point

distance to the closest object that can be seen clearly

hyeropia

farsightedness; refractive error that does not allow the eye to focus on nearby objects

Myopia (nearsightedness)

focal point is in front of the retina corrected with a concave lens

a real image must be projected onto the light-sensitive retina, which lies @ a fixed distance from lens

for clear vision...

photoreceptors

light-sensing cells; respond to light

numerical aperture

measure of a lens ability to "capture" light coming from the specimen and use it to make the image

accommodation

the process by which the eye's lens changes shape to focus near or far objects on the retina

Reflector telescope

A telescope that uses a large mirror to reflect and focus light.

1. objective lens 2. eyepiece (ocular)

2 convex lenses that make up a microscope

rods and cones

2 types of photoreceptors in the retina

The shape of the eye lenses became more convex as the finger moved toward his face

A boy stretches out his arm and focuses on a finger held at arm's length. He maintains his focus on the finger as he slowly moves it toward his face until it is just 15 cm from his eyes. Describe how the shape of his eye lenses changed as his finger moved toward his face.

chromatic abberation

A given convex lens has a focal length that varies slightly with the wavelength of the light passing through it. When the a lens is used as the objective of a telescope, this results in

concave lens (diverging lens)

A lens that is thinner in the middle, causing parallel rays of light to diverge (spread out) from a focus on the same side of the lens that the object is. The focal length of a diverging lens is negative. *causes light to bend away from its axis

diverging

A person who is "near-sighted", or myopic, cannot focus on faraway objects (objects at infinity) because the curvature of the person's eye-lens is too great. This causes parallel rays (from a distant point source) to bend too much and focus in front of the retina. The person sees a fuzzy patch of light rather than a sharp point. This person needs eyeglasses with lenses that are

converging lens

A person's image appears on the far side of an optical instrument, upside down. What is the optical instrument?

diverging with focal length equal to 20 cm.

A prescription for corrective lenses reads -5 D for each lens. These corrective lenses are

Refractive index varies with wavelength. White light is made up of all the wavelengths of visible light. This causes white light to be somewhat dispersed by a lens, resulting in each color having a different focal point

Describe the cause and result of chromatic aberration

The light coming from the object toward the observer's eye is bent away from the normal as it passes from water to air. The eye follows the refracted ray, but the brain does not know the light has been bent and thinks the object is located at a point in line with the ray. That point is above the object, because the ray was bent toward the surface of the water. The image of the object, therefore, appears to be above the object and at a more shallow depth.

Explain why an object in water always appears to be at a depth that is more shallow than it actually is

the path taken by a light ray always minimizes the time between any two points

Fermat's principle states that

Circle of least confusion

The minimum spot of light in the Interval of Sturm lying between the two line images of a spherocylinder.

The outer edges of the lens produce a focus at a different point from that formed by the central portion of the lens.

What causes spherical aberration?

black *A red object will only reflect red light. If a different color shines on the red object, no light is reflected, and the object will appear black.

What color would a red apple appear to be if you shine a blue light on it?

a, c, f

Which of the following statements are false for a single diverging lens? (a) A diverging lens is thicker at the center than it is at the edges.(b) A diverging lens only produces virtual images.(c) A diverging lens can produce images which are both magnified and reduced in size. (d) A diverging lens only produces upright images.(e) A diverging lens has a negative focal length. (f) The images formed by a diverging lens can be located on either side of the lens relative to the object.

The index of refraction depends on wavelength, but the the law of reflection does not. *A chromatic aberration occurs when different wavelengths of light focus at different places and with different magnifications

Why do lenses but not mirrors have chromatic aberration?

The stream appears shallower than it really is

You are looking at the bottom of a clear stream...

spherical aberration

a blurring of the periphery of an image as a result of inadequate reflection of parallel beams at the edge of a mirror or inadequate refraction of parallel beams at the edge of a lens

Astigmatism

a condition in which the eye does not focus properly because of uneven curvatures of the cornea

virtual image

a flat mirror creates a...

convex lens (converging lens)

a lens shaped so that all light rays that enter it parallel to its axis or another at a single point on the opposite side of the lens

thin lens

a lens whose thickness allows rays to refract but does not allow properties such as dispersion take place or aberrations

paraxial ray

a ray that moves nearly parallel to the optical axi

Refractor telescope

a telescope that uses only lenses to concentrate the light from an object and focus it into an image

coma

an aberration caused by an object that is off-center, often resulting in a pear-shaped image. The rays originate from points that are not on the optical axis and do not converge at a common focal point.

virtual image

an image that is on the same side of the lens as the object and can't be projected on the screen

acuity

sharpness of vision

cornea + lens

single thin lens consists of ....

real image

the image in which light rays from one point on the object actually cross at the location of the image, can be projected onto a screen/piece of film/the retina

focal point

the point at which rays parallel to the optical axis reflect and meet