Option C Imaging Flashcards

1
Q

How do you draw the rays in a ray diagram (for lenses, mirrors too?)

A

Straight through lens (doesn’t change)
Parallel —> focal point
Focal point —> parallel
(When focal point always think which one (does it diverge or converge?), also not always actually through, but behaves as though through/from/to)

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2
Q

(Convex/Converging lens) If object within (closer than) the focal length, the image will be:

A

Virtual

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3
Q

Focal length

A

Distance from centre of lens to focal point

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4
Q

Convex Converging lens focal length neg or pos?

A

Focal length is ALWAYS POSITIVE
(Doesn’t matter on which side of the lens, always pos for converging lens)

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5
Q

Focal length neg or pos for concave diverging lens?

A

ALWAYS NEGATIVE!
Put -f in formula

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6
Q

Sign of focal length only dep the type of lens!!

A

Converging convex = POs
Diverging concave = neg

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7
Q

Object distance

A

Distance between the lens and object

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8
Q

Is object distance (do) POs neg?

A

Object distance always positive UNLESS multiple lenses, then could be neg

So basically ALWAYS POSITIVE FOR A SINGLE LENS (no matter concave or convex)

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9
Q

Image distance

A

Distance between centre of lens and image PARALLEL TO THE PRINCIPAL AXIS

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10
Q

What does the sign of the M (angular magnification) tell you about the image?

A

Whether it is up or down.

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11
Q

Positive M (due to neg di(not nec???)) means the image is

A

Right side up (not flipped). Not inverted

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12
Q

Neg M (pos di) means the image is

A

Upside down// image is inverted

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13
Q

What is the near point?

A

The smallest distance at which an object can be placed in order for the eye to form a clear image without straining. Generally said to be 25cm. (Double check if this is all)

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14
Q

What is the far point?

A

The furthest distance an object can be at to still see it/form a clear image of it (?) in theory infinity.

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15
Q

Image distance positive when

A

Image distance on OPPOSITE SIDE of the lens as the OBJECT distance
//
If image distance/image on the SAME SIDE AS THE EYE

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16
Q

Image distance neg when

A

Image distance on SAME SIDE of the lens as the OBJECT distance
//
If image distance/image on the OPPOSITE SIDE AS THE EYE

17
Q

What does angle of incidence tell you about the reflected ray?

A

Angle of incidence=angle of reflection.
Angle is between light ray and normal

18
Q

What do dotted lines mean in a ray diagram?

A

Not real, virtual, rays.

19
Q

Focal point in relation to centre of curvature (mirrors)

A

Centre of curvature = 2f
Or focal point = half C

20
Q

How do you draw ray diagram for concave mirror?

A

Top of object parallel to mirror (reflected) then —> through focal point. (If ray parallel, will go through focal point when reflected)
From top of object through the focal point, reflect, —> parallel

OBS IF THÉ OBJECT IS NOT ON THE PRONCIPAL AXIS, YOU MUST ALSO DRAW FROM THE BOTTOM OF THE IBJECT!!!!!

21
Q

Image of concave mirror w object outside of focal length, further away or at c

A

Inverted (smaller at far distance, but at C same size I think and approaching focal length increases in size (larger than object))

22
Q

Concave mirror object IN (closer than) focal length: image?

A

Parallel to focal fine
Focal —> parallel: go “from behind” through focal then object then image
Lines diverge, draw dotted virtual “into” the mirror,
VIRTUAL, LARGER, UPRIGHT image.

23
Q

Convex mirror ray diagram

A

Top of object
Parallel —> focal point
Focal point —> parallel
(Not actually through f, virtual lines)
Divergence outside mirror, convergence virtual, virtual upright smaller image (at least in the example)
Double check so that angle incidence = angle reflection

24
Q

Does the thin lens formula (1/f = 1/do + 1/di) tell you anything about size of the image//object or non-horizontal distances

A

ONLY GIVES HORIZONTAL DISTANCES!
To know heights use angular magnification formula M = - di/do

25
Q

What causes spherical aberration?

A

Light rays have slightly different focal lengths depending on the distance between the point they enter the lens to the principal axis.

Occurs because rays that enter the lens far from the principal axis have a slightly different focal length from rays entering near the axis.

26
Q

Is spherical aberration for lenses AND mirrors?

A

YES!!

27
Q

How can you reduce the impacts/fix spherical aberration?

A
  1. Stopping down — reducing aparture (diameter) of the lens — less light coming in, closer together/less distance from principal axis.
  2. Aspherical lens; Parabolic mirror
28
Q

Does chromatic aberration affect both lenses and mirrors?

A

NO!!!!!!! Chromatic only affects lenses!!! NOT mirrors.

29
Q

What causes chromatic aberration?

A

Arises because the lens has different refractive indices for different wavelengths. Thus there is a separate focal length for each wavelength (color) of light.

Different wavelength of light (color) would have different refractive indices so they would have different focal lengths.

30
Q

How do you reduce the impact of chromatic aberration?

A
  1. Use monochromatic light
  2. Combining lenses (achromatic doublet) (Different refractive index)
31
Q

What is the general equation for a microscope? (NOT IN FB: MEMORIZE!)

A

M =(ça, appr equal to)= mo * me * D/v2
Ang magn approx equal to linear magn objective lens times linear magn eyepiece lens times D/v2
D=near point v2=image distance (actual image), measured parallel to the principal axis!!

32
Q

What is the equation for angular magnification microscope at normal adjustment (SPECIAL CASE)? (That is; the image is formed at the near point)

A

M (approx equal to) mo * (D/fe + 1)

(D/f + 1) is in the FB = M so
M = mo * me Replace me by ^^

Also note that the linear and angular magnification of the eyepiece lens are the same

33
Q

What is the sign of ve and vo (object distances) for MICROSCOPES?

A

Ve = NEGATIVE!!! Final image and “object” in eyepiece are on the SAME SIDE. Virtual image
Vo = POSITIVE! Real image.

34
Q

What lenses do microscopes and telescopes consist of?

A

2 convex converging lenses

35
Q

Idk expl how refractive telescope works. Normal adjustment

A

Since the object very far away (infinity) the image produced by the objective lens is at the focal plane of the objective, and this image is then magnified by the eyepiece lens. The eyepiece lens forms a virtual, inverted image of the object. The final image is produced at infinity. The distance between the two lenses is the sun of their focal lengths. Normal adjustment is these conditions^^

36
Q

What is the distance between the lenses in telescope and what do you want the focal lengths to be like?

A

The distance is the sun of their focal lengths.
In a telescope we want an objective w long focal length and an eyepiece w a short focal length.

37
Q

Differentiate Newtonian and Cassegranian telescopes

A

Newtonian: concave mirror (sphere or parabolic) as main; plane mirror at 45deg that is not part of magnifying; image viewing through eyepiece on side; less compact telescope

Cassegrain: concave parabolic mirror as main; secondary is small convex mirror which deflects the image back down the tube through a hole in the primary mirror and contributes to the magnification; view through eyepiece at the back of the telescope; more compact than Newtonian

38
Q

Differentiate between earth-based and satellite-borne telescopes

A

Satellite: can make observations using the full electromagnetic spectrum. Do not suffer from light pollution. Are not affected by disturbances in the atmosphere. Building costs are much higher and that for bringing into orbit and controlling remotely. Needs to be able to withstand much higher temperature changes. Difficult to do remote repairs. Operational time 24h (earth only at night)

Earth based:

39
Q

Advantages and disadvantages//differentiate deflecting and refracting e telescopes

A

Reflecting use mirrors rather than lenses and thus have advantages over refractive:
Easier to make large mirrors that don’t break easily than large lenses (to see distant faint objects this is needed)
MIRRORS DONT SUFFER FROM CHROMATIC ABERRATION
Only one side has to be round in comparison to 2 on lenses