Ch. 2 - Physical Optics

Question 1

a region of approximation in which the wavelength is considered to be negligible compared with the dimensions of the relevant components of the optical system.

Answer 1

Geometrical Optics

Question 2

When the wave character of the light

may not be so ignored, the field is known as…

Answer 2

Physical Optics

Question 3

bending of light waves around the edges of an obstruction

Answer 3

diffraction.

Question 4

Law of Reflection

Answer 4

When a ray of light is reflected at an interface dividing two optical media, the reflected ray remains within the plane of incidence, and the angle of reflection equals the angle of incidence The plane of incidence is the plane containing the incident ray and the surface normal at the point of incidence.

Question 5

Law of Refraction (Snell’s Law)

Answer 5

When a ray of light is refracted at an interface dividing two transparent media, the transmitted ray remains within the plane of incidence and the sine of the angle of refraction is directly proportional to the sine of the angle of incidence

Question 6

Principle of Reversibility

Answer 6

Fermat’s principle of least time must predict the same path as determined for the original direction of light propagation. In general, then, any actual ray of light in an optical system, if reversed in direction, will retrace the same path backward.

Question 7

specular reflection

Answer 7

reflection from a perfectly smooth surface

all rays of a parallel beam incident on the surface obey the law of reflection from a plane surface and therefore reflect as a parallel beam;

Question 8

diffuse reflection

Answer 8

reflection from a granular or rough surface.

the law of reflection is obeyed locally for each ray, the microscopically granular surface results in rays reflected in various directions and thus a diffuse scattering of the originally parallel rays of light.

Question 9

total internal reflection

Answer 9

For angles of incidence θ(1) > θ (c) the incident ray experiences total internal reflection

Question 10

A sequence of events is ______ if the events occur regularly, or at equal time intervals.

Answer 10

isochronous

Question 11

According to Macaluso Physics, what did Fermat really mean?

Answer 11

Not minimize optical path time, optimize optical path length.

Question 12

In refraction, what is constant?

Answer 12

E=hf always true

Energy and Frequency always conserved
c/λ or v/λ constant.

Question 13

index of refraction will vary based on…

Answer 13

λ, wavelength.

Question 14

In imaging systems, the image is never a perfect copy of the object. Why? How?

Answer 14

1) Mirrors scatter (even if only to a small degree)
2) Aberrations (n∝λ)
3) Light is a wave! Diffraction
4) Losses
* mirrors not 100% reflective
* lens not 100% transmittive

As a result, image is distorted or less intense.

Question 15

system aberrations

Answer 15

when the optical system itself cannot produce the one-to-one relationship between object and image rays required for perfect imaging of all object points.

Question 16

diffraction limited

Answer 16

Even if the image were otherwise perfect,
the effect of using a limited portion of the wavefront leads to diffraction and a blurred image

Disappear completely for geometrical objects

Question 17

Cartesian surfaces

Answer 17

Reflecting or refracting surfaces that form perfect images

Question 18

hyperboloid

ellipsoid

Answer 18

Cartesian surfaces that render every object ray parallel after the first refraction. Such rays incident on the second surface can then be refracted again to form an image. Depending on the relative magnitudes of the refractive indices, the appropriate refracting surface is either a

hyperboloid – n(i)>n(0)
ellipsoid – n(0)>n(i)

Question 19

this cartesian surface images O at I by refraction.

Answer 19

Cartesian Ovioid

Question 20

The larger the actual object, the _____ precise is its image.

Answer 20

less

Question 21

Why are spherical optical surface most common?

Answer 21

Because images of actual objects are not free from aberrations and because hyperboloid surfaces are difficult to grind exactly

Spherical aberrations so introduced are accepted as a compromise when weighed against the relative ease of fabricating spherical surfaces.

Question 22

Can a plane surface be modeled as a cylindrical or spherical optical surfaces?

Answer 22

plane surface can be treated as a special case of a cylindrical or a spherical surface in the limit that the radius of curvature, R, of either type of surface tends to infinity.

Question 23

When the lengths are measured in meters, their reciprocals are said to have units of…

Answer 23

diopters

Question 24

explain the nearsighted eye

Answer 24

the refracted (converging) power of the eye is too great, so that a real image is formed in front of the retina. By reducing the convergence with a number of diverging lenses placed in front of the eye, until an object is clearly focused, an optometrist can determine the net diopter specification of the single corrective lens needed by simply adding the diopters of these test lenses.

Question 25

explain the farsighted eye

Answer 25

the natural converging power of the eye is not strong enough, and additional converging power must be added in the form of spectacles with a converging lens.

Question 26

a spherical lens is said to be stigmatic because…

Answer 26

rotational symmetry about optical axis allows a spherical lens to produce a point image of a point object

Question 27

a cylindrical lens is said to be astigmatic because…

Answer 27

lack rotational symmetry about optical axis, allowing a cylindrical lens to produce a line image of a point object.