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LC Physics > Light 1: Geometrical Optics > Flashcards

Light 1: Geometrical Optics Flashcards

https://www.625points.com/wp-content/uploads/2019/03/Leaving-Cert-Physics-Optics.pdf

1
Q

Define light

A
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2
Q

What constant speed does light travel at?

A
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3
Q

What is the difference between luminous and non- luminous?

A
  • Luminous objects emit their own light
  • Non- luminous objects reflect light which shines on them
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4
Q

How do we know that light is a form of energy?

A

We know that light is a form of energy because otherwise, the principle of conservation of energy would be violated:

  1. Other forms of energy are required to produce light. Think of the electrical to light conversion in the light bulb.
  2. Light can be converted into other forms of energy. Think of the solar panel or the Crookes’ radiometer.
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5
Q

How do we know that light travels in straight lines?

A

We know that light travels in straight lines because:

  1. Shadows (the principle behind the operation of sundials).
  2. The ‘cardboard hole’ demonstration.
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6
Q

Define light ray

A

A light ray is a straight line with an arrow that shows the direction in which light is travelling

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7
Q

Define beam

A

A number of rays together is called a beam

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8
Q

Name and explain 3 types of beam

A
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9
Q

REFLECTION

A
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10
Q

Define reflection of light

A

The reflection of light is the bouncing of light off an object

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11
Q

Name and explain 2 types of light reflection

A
  • Diffuse reflection: if the surface on which the light shines is rough (as are most surfaces), then the reflected light is scattered in all directions.
  • Regular reflection: if the surface on which the light shines is silvered and polished smooth, then the light is reflected in a regular manner (i.e. all the reflected rays have common characteristics)
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12
Q

Define:

  • Incident ray
  • Reflected ray
A
  • Incident ray: the name given to the ray approaching the mirror.
  • Reflected ray: the name given to the ray leaving the surface of the mirror.
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13
Q

Define:

  • Point of incidence
  • Normal at the point of incidence
A
  • Point of incidence: the name given to the point at which the ray strikes the mirror.
  • Normal at the point of incidence: the name given to an imaginary line which passes through the point of incidence, and is perpendicular to the surface of the mirror.
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14
Q

Define:

  • Angle of incidence
  • Angle of reflection
A
  • Angle of incidence: the name given to the angle between the incident ray and the normal at the point of incidence.
  • Angle of reflection: the name given to the angle between the reflected ray and the normal at the point of incidence.
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15
Q

What are The Laws of Reflection of Light:

A

The Laws of Reflection of Light:

  1. The incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane.
  2. The angle of incidence is equal to the angle of reflection.

i = r

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16
Q

IMAGES

A
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17
Q

What are the two types of images a mirror can form?

A
  1. Real images: are formed by the actual intersection of light rays.

Such images can be located on a screen or by the method of ‘no parallax’

  1. Virtual images: are formed by the apparent intersection of light rays. They appear to intersect (but don’t actually)

Such images can never be formed on a screen, but they can be located by the method of ‘no parallax’.

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18
Q

Can real images be formed on a screen?

Can virtual images be formed on a screen?

A

Yes

No

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19
Q

What are two features of a virtual image in a plane mirror?

A

A virtual image in a plane mirror is:

  1. On the perpendicular from the object to the mirror.
  2. The same distance behind the mirror as the object is in front.
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20
Q

Define lateral inversion

A

Lateral inversion: in a mirror all reflected objects are inverted from right to left. (e.g. The word AMBULANCE is written in reverse so drivers can read it in their mirrors.).

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21
Q

Define parallax

A
  • Parallax is the apparent movement of one object relative to another due to the motion of the observer
  • The object that is furthest away appears to move with the observer.
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22
Q

What does it mean when an object is in the State of No Parallax?

A

If there is no parallax between two objects, then

  • In the same line of sight.
  • At the same distance from the observer.
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23
Q

SPHERICAL MIRRORS

A
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24
Q

Name and explain the two types of spherical mirror

A
  • Concave mirror: the reflecting surface is located on the ‘inside bend’.
  • Convex mirror: the reflecting surface is located on the ‘outside bend’.
25
Q

Explain what:

  1. C
  2. P
  3. axis
  4. F
  5. f

refer to

A
  1. Centre of curvature: is the centre of the sphere from which the mirror is made. Denoted by C.
  2. Pole: is the centre of the spherical mirror. Denoted P.
  3. Principal axis: is the straight line joining the pole to the centre of curvature. Also referred to simply as the ‘axis’.
  4. Focus/focal point: is the point midway between the centre of curvature and the pole. Denoted F.
  5. Focal length: is the distance between the focus and the pole. Denoted f.
26
Q

Define magnification

A

Magnification: is the ratio of the height of the image to the height of the object.
Denoted m.

27
Q

CONCAVE MIRROR

A
28
Q

For reflection in concave mirrors, the normal at the point of incidence will always pass
through the _________________.

A

Centre of curvature

29
Q

For reflection in concave mirrors, what happens if the ray passes through the entre of curvature?

A

In through C, out through C: a ray which passes through the centre of curvature and then strikes the mirror is reflected back along its own path.

30
Q

For reflection in concave mirrors, what happens if the ray strikes the pole?

A

Strikes pole, equal angles: a ray that strikes the pole is reflected at an equal angle with the axis.

31
Q

For reflection in concave mirrors, what happens if the ray comes in parallel to the axis

A

In parallel, out through F: a ray which comes in parallel to the axis passes through the focus after reflection at the mirror.

32
Q

For reflection in concave mirrors, what happens if the ray which passes through the focus?

A

In through F, out parallel: a ray which passes through the focus and then strikes the mirror is reflected out parallel to the axis.

33
Q

For a concave mirror:

  • If the object is outside the focus the image is __________.
  • If the object is inside or at the focus the image is __________.
A

For a concave mirror:

  • If the object is outside the focus the image is real and located in front of the mirror.
  • If the object is inside or at the focus the image is virtual and is located behind the mirror.
34
Q

What does it mean if an object is a large distance from a concave mirror?

A

Image of a Distant Object in a Concave Mirror:

  • If an object is a large distance from a concave mirror, then the image is real and located at the focus.
  • This is because light from any point on a distant object arrives as a beam of parallel light.
35
Q

What are the formulae for a concave mirror?

A
36
Q

CONVEX MIRROR

A
37
Q

For reflection in convex mirrors, the normal at the point of incidence will always pass
through the _________________.

A

Centre of curvature

38
Q

What are the convex mirror special cases?

A
  • These are very similar to what happens with a concave mirror.
  • The only difference is that light rays which are reflected in a convex mirror can never actually pass through C or F.
  • In through C, out through C: A ray that comes in as if to hit C will be reflected back along its path as if it came out through C.
  • In parallel, out through F: A ray that goes in parallel will come out as if it has passed through F.
  • In through F, out parallel: A ray that goes in as if it will hit F will come out parallel.
39
Q

Describe two features of images in convex mirrors.

A

For a convex mirror:

  • The image is always virtual and located behind the mirror.
  • The image is always diminished. The nearer the object is to the mirror the bigger the image.
40
Q

What is the formula for a convex mirror?

A
41
Q
  • All distances to real objects and images are ________.
  • All distances to virtual objects
    and images are ________.
A

Real is Positive - Virtual is Negative Rule:

  • All distances to real objects and images are positive
  • All distances to virtual objects
    and images are negative.
42
Q
  • The focal length of a ________ mirror is positive.
  • The focal length of a ________ mirror is negative.
A
  • The focal length of a concave mirror is positive.
  • The focal length of a convex mirror is negative.
43
Q
  • What do u, v and f stand for?
  • When is each positive and negative?
A
44
Q

IMAGES IN CONCAVE MIRRORS

In all that follows, the black and green lines represent two distinct light rays which is the minimal amount required for the formation of an image. The blue arrow 1 represents the object, and the red arrow 1 the image formed as a result of reflection in the mirror.

A
45
Q

When the object is outside C, the image is:

(a) real;

(b) inverted;

(c) diminished;

d) formed between C and f.

A
46
Q

When the object is at C, the image is:

(a) real;
(b) inverted;

(c) the same size as the object;

(d) formed at C.

A
47
Q

When the object is between C and f, the image is:

(a) real;
(b) inverted;
(c) magnified;
(d) formed outside C.

A
48
Q
  1. When the object is at f, the image is formed at infinity. This means that the rays are parallel so they never meet to form an image

(Parallel lines do actually meet at infinity; for instance, train tracks appear to converge at the horizon.
See projective geometry for more on this.)

A
49
Q
  1. When the object is inside f, the image is:

(a) virtual;
(b) erect;
(c) magnified;
(d) formed behind the mirror.

A
50
Q

IMAGES IN CONCAVE MIRRORS

There is only one case to consider as reflection only occurs when the object is located on the side of the mirror opposite f and C. The image is:

(a) virtual;
(b) erect;
(c) diminished;
(d) formed behind the mirror.

A
51
Q

REFRACTION

A
52
Q

Define refraction

A

Refraction is the bending of a ray of light as it passes from one transparent medium to another.

53
Q

When does no refraction occur?

A

o refraction occurs if the ray strikes the second medium at right angles.

54
Q

Define:

  • Incident ray
  • Reflected ray
A

Incident ray: the ray of light striking the second medium.

Refracted ray: the ray of light travelling through the second medium.

55
Q

Define:

  • Point of incidence
  • Normal at the point of incidence
A

Point of incidence: the point at which the incident ray strikes the second medium.

Normal at the point of incidence: the imaginary line through the point of incidence, and perpendicular to the boundary between the two media.

56
Q

Define:

  • Angle of incidence
  • Angle of refraction
A

Angle of incidence: the angle between the incident ray and the normal at the point
of incidence. Denoted i.

Angle of refraction: the angle between the refracted ray and the normal at the point of incidence. Denoted r.

57
Q
A

Refraction will only occur if the speed of light in the second medium is different from the
speed of light in the first.

58
Q
A

LC Physics (1 decks)

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