Ch 8 - Light and Optics Flashcards

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1
Q

electromagnetic spectrum from lowest energy to highest energy

A

radio waves (wavelength range from 10^9 - 1 m), microwaves (1 m - 1 mm), infrared (1 mm - 700 nm), visible light (700 nm - 400 nm), ultraviolet (400 - 50 nm), x-rays (50 - 10^-2 nm), gamma rays (less than 10^-2 nm)

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2
Q

electromagnetic waves

A

transverse waves - oscillating electric and magnetic field vectors are perpendicular to the direction of propagation and each field is perpendicular to each other.

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3
Q

common units of wavelength

A

mm (10^-3 m), fancy um (mu) (10^-6 m), nm (10^9 m) and A with a circle at the point (angstrom, 10^-10 m)

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4
Q

visible spectrum from lowest to highest energy

A

Red, orange, yellow, green, blue, violet (roy g bv)

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5
Q

speed of light

A

EM waves travel this fast in a vacuum and in air: c = 3.00 x 10^8 m/s

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6
Q

equation for speed of light

A

c = f x wavelength; f = frequency; c = speed of light in air and vacuum

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7
Q

approximate wavelength boundaries of the visible spectrum

A

400-700 nm

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8
Q

blackbody

A

ideal absorber of all wavelengths of light, which would appear completely back if it were at a lower temp than its surroundings

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9
Q

rectilinear propagation

A

concept that light travelling through a homogenous medium will travel in a straight line

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10
Q

reflection

A

rebounding of incident light waves at the boundary of a medium

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11
Q

law of reflection

A

theta sub 1 = theta sub 2 (angles of reflection); theta sub 1 = angle of incident and theta sub 2 = reflected angle

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12
Q

normal (in reference to reflection)

A

a line drawn perpendicular to the boundary of a medium; all angles in optics are measured from the normal, not the surface of the medium

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13
Q

real image

A

image in which the light actually converges at the position of the image; this image can be projected onto a screen

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14
Q

virtual image

A

image in which the light only appears to be coming from the position of the image but does not actually converge there

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15
Q

plane mirrors

A

flat reflective surfaces that cause neither convergence nor divergence of reflected light rays; because light does not converge at all, these always created virtual images because reflected light remains in front of the mirror but the image appears behind the mirror

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16
Q

spherical mirrors

A

come in two varieties: concave and convex and have associated center of curvature (C) and radius of curvature (r)

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17
Q

center of curvature

A

point on the optical axis located at a distance equal to the radius of curvature from the vertex of the mirror; the center of the spherically shaped mirror if it were a complete sphere

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18
Q

concave mirror

A

also called converging mirrors; edges coming towards you; center of curvature and radius of curvature are located in front of the mirror

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19
Q

convex

A

also called diverging mirrors; surface coming towards you; edges away; center of curvature and radius of curvature are behind the mirror

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20
Q

focal length (f) of mirror

A

distance between focal point (F) and mirror

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21
Q

focal length for spherical mirror

A

f = r/2 where radius of curvature (r) is distance between C (center of curvature) and the mirror

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22
Q

relationship between four important distances of spherical mirrors

A

1/f = 1/o + 1/i = 2/r; where f = focal length, o = distance between object and mirror, i = distance between image and mirror, r = radius of curvature

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23
Q

image distance greater than 0

A

real image which implies that the image is in front of the mirror

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24
Q

image distance less than 0

A

virtual image; image is behind the mirror

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25
Q

magnification (m)

A

dimensionless value that is the ratio of the image distance to the object distance (m = -i/o); also gives ratio of the size of the image to the size of the object

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26
Q

inverted image

A

negative magnification value

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27
Q

upright image

A

positive magnification value

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28
Q

what happens to image where |m| < 1

A

image is smaller than object

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29
Q

what happens to image if |m| > 1

A

image is larger than the object

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30
Q

what happens if image is |m| = 1

A

image is same size as object

31
Q

ray diagram

A

gets approximations of where an image is using o, C, F, and I

32
Q

axis

A

the normal passing through the center of the mirror

33
Q

converging (concave mirror): if object is between focal point and mirror

A

image is virtual, upright and magnified

34
Q

converging (concave mirror): if object is beyond focal point

A

image is real, inverted and magnified

35
Q

converging (concave mirror): if object is placed at focal point

A

no image is produced. i = infinity

36
Q

image produced by diverging mirror

A

virtual, upright and reduced only

37
Q

when i is positive or negative

A

positive i indicates image is in front of mirror (real); negative indicates image is behind mirror (virtual)

38
Q

when o is positive or negative

A

positive indicates object is in front of mirror; negative is very rare and indicates object is behind mirror

39
Q

when r is positive or negative

A

positive radius indicates mirror is concave (converging); negative indicates mirror is diverging (convex)

40
Q

when f is positive or negative

A

positive indicates mirror is concave (converging); negative indicates mirror is convex (diverging)

41
Q

when m is positive or negative

A

positive indicates image is upright (erect); negative indicates image is inverted

42
Q

refraction

A

bending of light as it passes from one medium to another and changes speed; speed is always less than through a vacuum

43
Q

Snell’s Law

A

when light is in any medium besides a vacuum speed is less than c and is given by n = c/v; where c = speed of light in vacuum, v = speed of light in the medium, and n = dimensionless quantity called index of refraction of the medium

44
Q

equation relating to Snell’s Law as light passes from one medium to another

A

n sub 1 sin theta sub 1 = n sub 2 sin theta sub 2; n sub 1 = index of refraction of medium from which the light is coming and theta sub 1 = angle of refraction in reference to the normal from this medium and sub 2 = same of medium to which light is going

45
Q

critical angle

A

theta sub c; angle at which refracted angle (theta sub 2) = 90 degrees; refracted light ray passes along the interface between the two media

46
Q

critical angle equation

A

theta sub c = sin^-1 ((n sub 2)/n sub 1);

47
Q

total internal reflection

A

phenomenon in which all the light incident on a boundary is reflected back into the original material; results with any angle of incidence greater than the critical angle (theta sub c)

48
Q

difference between lenses and mirrors

A

lenses refract light while mirrors reflect it; also lenses have two surfaces that affect the light path: from an object through the air into the glass lens (first surface); and through the glass until it reaches the other side, where again it travels out of the glass and into the air (second surface); two focal points and focal length can be measured in either direction from the center

49
Q

thin spherical lens focal length

A

have one focal length because the two are the same to one side and the other

50
Q

formulas for finding distance and magnification for thin spherical lenses

A

1/f = 1/o + 1/i = 2/r and m = -i/o. f = focal length, o = object distance, i = image distance, m = magnification

51
Q

real lens focal length (lensmaker’s equation)

A

1/f = (n - 1) ((1/r sub 1) - (1/ r sub 2)); n = index of refraction for lens material; r sub 1 = radius of curvature for first lens surface; r sub 2 is for second lens surface

52
Q

meaning when o is positive or negative for single lenses

A

positive means object is on same side of lens as light source; negative means object is on opposite side of lens (extremely rare)

53
Q

meaning when i is positive or negative for single lenses

A

positive means image is on opposite side of lens from light source (real); negative means image is on same side as light source (virtual)

54
Q

meaning when r is positive or negative for single lenses

A

positive means lens is convex (converging); negative means lens is concave (diverging)

55
Q

meaning when f is positive or negative for single lenses

A

positive means lens is convex (converging); negative means lens is concave (diverging)

56
Q

meaning when m is positive or negative for single lenses

A

positive means image is upright (erect); negative means image is inverted

57
Q

Power of lens

A

measured in diopters: P = 1/f; where f = focal length and is in meters; P is positive for converging lens and negative for diverging

58
Q

nearsighted people need

A

diverging lenses (nearsightedness is myopia)

59
Q

farsighted people need

A

converging lenses (farsightedness is hyperopia)

60
Q

focal length of multiple lenses in system

A

1/f = 1/f sub 1 + 1/f sub 2 + 1/f sub 3 …. etc

61
Q

power of multiple lenses in system

A

P = P sub 1 + P sub 2 etc

62
Q

magnification for multiple lens systems

A

m = m sub 1 x m sub 2 … etc

63
Q

aberrations

A

specific types of errors found in mirrors and lenses

64
Q

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

65
Q

dispersion

A

when various wavelengths of light separate from each other

66
Q

chromatic aberration

A

dispersive effect within a spherical lens which causes a rainbow halo around images

67
Q

Diffraction

A

refers to spreading out of light as it passes through a narrow opening or around an obstacle

68
Q

location of dark fringes (minima) in diffraction

A

a sin theta = n x wavelength; a = width of the slit through which light is passing; theta = angle between line drawn from the center of the lens to the dark fringe and that axis of the lens; n = an integer indicating the number of the fringe; wavelength = incident wave

69
Q

interference

A

when waves interact with each other this is the process of the displacement of the waves added together

70
Q

positions of dark fringes (minima) on a screen

A

d sin theta = (n + (1/2)) x wavelength; d = distance between the two slits; theta = angle between the line drawn from the midpoint between the two slits to the dark fringe and the normal; n = integer indicating number of the fringe; wavelength is incident wave

71
Q

Diffraction gratings

A

consist of multiple slits arranged in patters; can create colorful patterns similar to a prism as the different wavelengths interfere in characteristic patterns

72
Q

light fringes

A

created from multiple slit systems; result from constructive and destructive interference between light rays

73
Q

plane-polarized light

A

also called linearly polarized light; light in which electric fields of all the waves are oriented in the same direction (their electric field vectors are parallel)