Optics Exam 1: Key Terms and Definitions for Success

What is the wavelength range for visible light?

400 to 740nm

What is the speed of light in a vacuum?

c=3x10^8 meters per second

What colors exhibit long and short wavelengths?

Red gives long wavelengths and short gives blue wavelengths

What gives an object it's surface color?

wavelengths that are reflected from or produced at a surface/sourse

What happens to light that is not reflected to transmitted?

it is absorbed

What are the colors you see?

colors that are not absorbed, but reflected back into your eye

EX: a blue shirt absorbs red wavelengths and reflects back blue wavelengths

Where does reflection occur?

at any boundary between two different media (EX: air/water or air/lens)

What are the two main/broad types of reflection?

specular and diffuse

What is a specular reflection?

a very smooth surface with a smooth reflection

What is a diffuse reflection?

a rough surface, where light is reflected at strange angles

Where does scattering occur?

non-homogenous optical media

index of refraction

n=c/v

velocity

v=c/n

n for materials other than air is always (greater than or less than) one

greater than one

Snell's Law

n₁sinθ₁=n₂sinθ₂

How does θ change as light travels from lower to higher index?

the angle decreases

How does θ change as light travels from higher to lower index?

the angle increase

What is a point source?

a source that emits light in all directions

-wavefronts are spherical

-short radius of curvature gives high wave front curvature

-long radius of curvature gives low wave front curvature

What is a converging wavefront and what is it's center of curvature?

-the center of curvature is the image point

-the rays meet here in a point image

-anywhere else, the image is a blur circle

What is a diverging wavefront and what is it's center of curvature?

the center of curvature is the source point (object point)

curvature of a sphere

1/radius of curvature

What is vergence?

the amount of convergence or divergence

vergence equation

Vergence = refractive index (n) / distance from object or image (r)

As diverging light travels, the distance from the source increases and vergence magnitude _________.

decreases

What is the sign for vergence of a converging ray?

positive vergence

What is the sign for vergence of a diverging ray?

negative vergence

What is a ray bundle?

a collection of rays traveling away from a point of object, or traveling towards a point on an image

What is an object at infinity?

parallel rays traveling away from an object

What is an image at infinity?

parallel rays traveling toward the image

What are object rays?

the rays arriving at a lens

What are image rays?

the rays leaving a lens

What is a real object?

diverging light from an object, arriving at a lens

What is the vergence for a real object?

negative

What is a real image?

converging light leaving the lens, towards the image (point at which all the rays intersect)

What is the vergence for a real image?

positive

What is a virtual image?

diverging light leaving a lens (does not converge to a point, cannot be formed on a screen)

What is the vergence for a virtual image?

negative

What is a virtual object?

converging light arriving at a lens

What is the vergence for a virtual object?

positive

What is the optical axis?

the line joining the centers of curvature of the two lens surfaces

What is the secondary focal point?

the on-axis image point for a distant on-axis object point

Where is F₂ for a converging lens?

to the right

What is the primary focal point?

the on-axis object point that produces an image at infinity

Where is F₁ for a converging lens?

to the left

What is the relationship of the focal points for a thin lens in air?

they are equidistant from the lens

For a diverging lens, shorter the focal length, the ____ the lens power.

higher

For a diverging lens, the further the focal length, the ____ the lens power.

lower

How are object distance measured?

From the lens to the object

How are image distances measured?

From the lens to the image

objects or images to the left of the lens...

-distance is negative

-vergence is negative

-objects are real

-images are virtual

objects or images to the right of the lens...

-distance is positive

-vergence is positive

-objects are virtual

-images are real

thin lens vergence equation

image vergence (V) = object vergence (U) + lens power (P)

lens power and focal length equation

f₁=-1/P or f₂=1/P

If U=0 then V=___

P

If U is negative, the object is _____.

real

If U is positive, the object is _____.

virtual

If V is positive, the image is ____.

real

If V is negative, the image is _____.

virtual

If U and P are both negative, then the image is ____.

virtual

If U and P are both positive, then the image is ____.

real

For a converging lens, the primary focal point is to the ___ of the axis.

left

For a diverging lens, the primary focal point is to the ___ of the axis.

right

For a virtual object and a converging lens, the image will be...

real

For a real object and a diverging lens, the image will be...

virtual

For a virtual object and a diverging lens, the image will be...

virtual

If the object is at F1, then the image is...

at optical infinity

If the object is inside F1, then the image is...

real

If the object and image have the same sign (both positive or both negative), then magnification will be...

positive

If the object and image have opposite signs, then magnification will be...

TERM

negative

If the image is smaller than the object, magnification will be greater than or less than 1?

less than 1

If magnification is 1, the object and image are...

the same size

A real object produces a ____ image on the retina.

real

What is the total power of a typical eye model?

+60D

What is the far point?

the object point that results in an image point on the retina

Where is the far point for emmetropes?

infinity

Describe a myopic eye.

too long or too strong

When myopes view distance objects, the image is focused (in front of/behind) the retina.

in front of

For myopes, the far point is always (in front of/behind) the eye.

in front of

For myopes, the far point is a (real/virtual) object point.

real

Describe a hyperopic eye.

too short or too weak

When a hyperope with relaxed accommodation views a distant object, the image is...

behind the retina

For hyperopes, the far point is always (in front of/behind) the eye.

behind

For hyperopes, the far point is a (real/virtual) object point.

virtual

For a myope, vergence LEAVING the eye is (converging/diverging).

converging

For a hyperope, vergence LEAVING the eye is (converging/diverging).

diverging

What is the definition of refractive error correction?

the vergence required to enter the eye to come to a focus on the retina

What is vertex distance?

distance from lens to cornea

For a myope, will their glasses or contact prescription be stronger? (more negative)

glasses

Where will a correcting lens' secondary focal point be?

at the eye's far point

What is lens effectivity?

the effectivity of a lens differs with vertex distance

Plus lenses (gain/lose) effectivity as vertex distance increase.

gain

Minus lenses (gain/lose) effectivity as vertex distance increase.

lose

What happens when the eye accomodates?

the lens changes shape and adds more positive dioptric power

When an object moves closer to the eye, there is (more/less) (positive/negative) object vergence.

more negative

When an object moves closer to the eye (more/less) accommodation is required.

more

What is the near point?

the point where the image is on the retina at maximum accommodation

The Ufp for myopia is always...

negative

The Unp for myopia is always...

negative

The Ao for myopia is always...

positive (or zero)

In myopia, the far point and near point will both be (in front of/behind) the eye.

in front of