# law of reflection

## reflected light and images

Reflection is one of several ways that light can interact with matter. Light reflects off surfaces such as mirrors that do not transmit or absorb light. When light is reflected from a smooth surface, it may form an image. An image is a copy of an object that is formed by reflected (or refracted) light. Q: Is an image an actual object? If not, what is it? A: No, an image isnt an actual object. It is focused rays of light that make a copy of an object, like a picture projected on a screen.

## regular and diffuse reflection

If a surface is extremely smooth, as it is in a mirror, then the image formed by reflection is sharp and clear. This is called regular reflection (also called specular reflection). However, if the surface is even slightly rough or bumpy, an image may not form, or if there is an image, it is blurry or fuzzy. This is called diffuse reflection. Q: Look at the boats and their images in the Figure 1.1. Which one represents regular reflection, and which one represents diffuse reflection? A: Reflection of the boat on the left is regular reflection. The water is smooth and the image is sharp and clear. Reflection of the boat on the right is diffuse reflection. The water has ripples and the image is blurry and wavy. In the Figure 1.2, you can see how both types of reflection occur. Waves of light are represented by arrows called rays. Rays that strike the surface are referred to as incident rays, and rays that reflect off the surface are known as reflected rays. In regular reflection, all the rays are reflected in the same direction. This explains why regular reflection forms a clear image. In diffuse reflection, the rays are reflected in many different directions. This is why diffuse reflection forms, at best, a blurry image.

## law of reflection

One thing is true of both regular and diffuse reflection. The angle at which the reflected rays leave the surface is equal to the angle at which the incident rays strike the surface. This is known as the law of reflection. The law is illustrated in the Figure 1.3.

## instructional diagrams

This diagram shows Ray (optics). In optics, a ray is an idealized model of light, obtained by choosing a line that is perpendicular to the wave fronts of the actual light, and that points in the direction of energy flow. Rays are used to model the propagation of light through an optical system by dividing the real light field up into discrete rays that can be computationally propagated through the system by the techniques of ray tracing. This allows even very complex optical systems to be analyzed mathematically or simulated by computer. All three rays should meet at the same point. The Principal Ray or Chief Ray (sometimes known as the b ray) in an optical system is the meridional ray that starts at the edge of the object and passes through the center of the aperture stop. This ray crosses the optical axis at the locations of the pupils. As such, chief rays are equivalent to the rays in a pinhole camera. The Central Ray is perpendicular to Infrared Radiation. The third one, called the Focal Ray, is a mirror image of the parallel ray. The focal ray is drawn from the tip of the object through (or towards) the focal point, reflecting off the mirror parallel to the principal axis.

This diagram explains the law of reflection and shows how light gets reflected from a surface. The law of reflection states that the angle of incidence (i) is always equal to the angle of reflection (r). The angles of both reflected and incident ray are measured relative to the imaginary dotted-line, called normal, that is perpendicular (at right angles) to the mirror (reflective surface).

The reflection of a tree shines in to the lake. When the human eye sees the reflection from the tree on the water it looks the right direction. The image of the tree is upside down. The water reflection on the lake makes things upright to the human eye.

This diagram depicts how light rays can reflect off various surfaces. Incident rays will reflect back at a specific angle if the surface is smooth. A rough or broken surface will have reflected rays with a wide variety of reflected angles. The left part of the diagram shows why your reflection in a mirror is smooth and natural looking.

## questions

when light reflects off a smooth surface, it forms a clear image.

``````-->  a. true

b. false
``````

the type of reflection described in question 3 is called

``````a) normal reflection.

b) diffuse reflection.

-->  c) regular reflection.

d) none of the above
``````

rays of light are reflected in many different directions in

``````a) specular reflection.

b) regular reflection.

-->  c) diffuse reflection.

d) all of the above
``````

the image formed when light rays are reflected as described in question 5 is blurry or fuzzy.

``````-->  a. true

b. false
``````

the angles of reflection and incidence are measured relative to a line that is parallel to the reflective surface.

``````a. true

-->  b. false
``````

## diagram questions

Which label represents a plane mirror?

``````a. R

b. K

-->  c. V

d. H
``````

Which label shows the Angle of reflection?

``````a. V

b. H

c. K

-->  d. R
``````

Which label marks the angle of reflection?

``````a. R

-->  b. M

c. N

d. H
``````

Where's the angle of incidence?

``````a. M

b. Y

c. N

-->  d. R
``````

Where is the incident ray?

``````a. N

-->  b. Y

c. M

d. H
``````

Which letter represents the Angle of incidence

``````a. A

b. H

-->  c. T

d. U
``````

Identify the incident ray in the following image:

``````a. A

-->  b. H

c. U

d. W
``````

Which phenomena is shown in the picture?

``````a. DIFFUSION

b. PARTIAL REFLECTION

-->  c. FULL REFLECTION

d. DIFFRACTION
``````

Which label refers to the incident ray?

``````a. E

b. F

c. T

-->  d. Y
``````

Which label shows the Incident Ray?

``````a. E

-->  b. Y

c. W

d. M
``````

Identify the incident ray

``````a. A

b. N

c. D

-->  d. Y
``````

Which label refers to the mirror?

``````a. D

-->  b. L

c. Y

d. A
``````

What phenomena can you see in the diagram?

``````-->  a. REFLECTION

b. DIFFUSION

c. REFRACTION

d. ECHO
``````

Where is the refracted ray in this picture?

``````a. H

b. K

-->  c. J

d. A
``````

The reflective ray is being illustrated by which letter?

``````-->  a. K

b. H

c. I

d. K
``````

By what letter is the angle of reflection represented in the diagram?

``````a. C

b. K

c. S

-->  d. D
``````

Which is the incident angle?

``````a. H

b. S

-->  c. T

d. D
``````

How many colors of arrows are shown in the picture?

``````a. 3

b. 1

c. 4

-->  d. 2
``````

What would happen to image if there was no plane mirror?

``````a. image would be formed far from the object

b. image would be formed near the eye

c. image would be formed right before object

-->  d. no image would be formed
``````

How many focal points are shown in this diagram?

``````-->  a. 2

b. 3

c. 4

d. 1
``````

How many focus point are there in a single convex lens as shown in diagram?

``````a. 1

b. 3

-->  c. 2

d. 4
``````

Identify the system drawn above.

``````a. Concave Lens

b. Mirror

c. Convex Lens

-->  d. Reflection
``````

What plane does an object cross over to become an image?

``````a. Regular Plane

b. Object Plane

c. Image Plane

-->  d. Principal Plane
``````

What do you call a plane that is perpendicular to the axis of a lens, mirror, or other optical system?

``````a. Focal Plane

-->  b. Principal Plane

c. Plane of an Image

d. Objective Plane
``````

What is the point in space where parallel light rays meet after passing through the lens or bouncing off the mirror?

``````a. convex lens

b. image

-->  c. focal point

d. principal axis
``````

What's the purpose of a convex lens?

``````a. To switch an image's orientation

b. To spread apart the rays of light that go through it

c. To make objects look smaller

-->  d. To bring together the rays of light that pass through the lens
``````

What is the distance between the len and the image formed?

``````a. F

b. Dh_ = do_+h_

-->  c. D

d. Do
``````

How many focal points are there?

``````a. 3

b. 4

c. 1

-->  d. 2
``````

The distance between object and image equals to:

``````-->  a. u+v

b. C

c. F_+F_

d. u-v
``````

How many rays pass through the lens without refraction?

``````a. 4

-->  b. 1

c. 3

d. 2
``````

Why does the ray 1 go straight through the lens at its center?

``````a. For reference

-->  b. Because the lens has no thickness

c. Because it's a convex lens

d. Because it's a concave lens
``````

How many points does the object rays have to intersect in the image plane after refraction to achieve focus?

``````a. 3

b. 4

c. 2

-->  d. 1
``````

The image produces are?

``````-->  a. Inverted and Magnified

b. Upright and Smaller

c. Upright and Magnified

d. Inverted and Smaller
``````

Where should the object be placed in front of a double convex lens to form a real image?

``````a. At the focal point (f)

b. All of the above

c. In front of the focal point (f)

-->  d. Beyond the focal point (f)
``````

How many items are labeled in the diagram?

``````a. 4

b. 5

-->  c. 2

d. 3
``````

The focal length is known as what symbol?

``````a. #

-->  b. f

c. @

d. h
``````

Which geometrical figure is formed in between ho, hl and ho where is hl=0?

``````-->  a. Triangle

b. Square

c. Circle

d. Rectangle
``````

What is the distance between the lens and the image sensor when the subject is in focus?

``````-->  a. Focal Length

b. Point

c. Focus Point

d. Focal Point
``````

What is the distance between the image and object?

``````a. o

-->  b. f

c. i

d. j
``````

How many parts are labeled in the diagram?

``````-->  a. 2

b. 4

c. 5

d. 3
``````

Would the image formed be erect?

``````-->  a. Yes

b. Data Insufficient

c. Can't say

d. No
``````

If the angle of incidence is increased what will happen to the angle of reflection?

``````a. Angle of reflection will increase by a greater degree

b. Angle of reflection will remain the same

-->  c. Angle of reflection will increase by the same degree

d. Angle of reflection will decrease
``````

What causes the reflected ray?

``````-->  a. The incident ray bouncing off the surface

b. The angle of incidence bouncing off the surface

c. Depends on the angle of the ray that bounces off the surface

d. On the angle of reflection
``````

If the angle of incidence in the diagram increases, what would happen to angle of reflection?

``````-->  a. angle of reflection also increases

b. not enough information

c. angle of reflection decreases

d. no change in angle of reflection
``````

Which angle is the result of a reflected ray?

``````-->  a. Angle of Reflection

b. Incident Ray

c. None

d. Angle of Incidence
``````

If an is the incident ray angle, |a| its absolute value and b the reflected ray angle, what would be |b|?

``````-->  a. |b|=|a|

b. |b|=|a|*sin(a)

c. |b|=-|a|

d. |b|=|a|^(-1)
``````

How many rays are shown in the figure?

``````a. 4

b. 1

-->  c. 3

d. 2
``````

How many reflected rays are in the diagram?

``````a. 3

b. 2

-->  c. 1

d. none
``````

As the diagram shows, the angle of incidence is always equal to which of the following?

``````a. The mirror angle

b. The normal angle

-->  c. The angle of reflection

d. The ray angle
``````

What light is bounced from the mirror?

``````a. normal

-->  b. reflected ray

c. microwave

d. incident ray
``````

How many arrows show the path of light?

``````a. 4

b. 1

-->  c. 3

d. 2
``````

How many reflected rays for one incident ray?

``````a. 4

b. 2

c. 3

-->  d. 1
``````

What measures the light falling on your subject?

``````a. Water

-->  b. Incident Light

c. Air

d. Reflected Light
``````

How many angles/s of reflection does the figure show?

``````a. 3

b. 4

-->  c. 1

d. 2
``````

How many angles there are?

``````a. 4

b. 5

c. 1

-->  d. 3
``````

If the angle of Incidence is made larger how would it affect the reflected ray?

``````a. It would become smaller

-->  b. It would become larger by the same amount.

c. It would disappear

d. It would stay the same
``````

What is this diagram all about?

``````a. Light

-->  b. Optics

c. Rays

d. Energy
``````

How many reflected rays are shown in the diagram?

``````a. 3

b. 1

c. 2

-->  d. 4
``````

Would this surface give a reflection?

``````a. Yes

b. Not enough information to know.

c. Probably

-->  d. No
``````

What rays reflect off of a surface?

``````a. Direct Rays

b. Incident Rays

-->  c. Reflected Rays

d. Indirect Rays
``````

How many arrows are going in for letter a?

``````-->  a. 4

b. 2

c. 3

d. 5
``````

Which shows a regular reflection?

``````a. C

-->  b. A

c. A and B

d. B
``````

What does the angle of incidence equal?

``````a. mirror

b. Reflected Ray

c. incident ray

-->  d. Angle of Reflection
``````

When an incident ray is reflected on a mirror, what is the resulting ray called?

``````-->  a. Reflected ray

b. Normal ray

c. Ray of incidence

d. Mirrored ray
``````

How many angles are at play when light hits a mirror?

``````-->  a. 2

b. 4

c. 3

d. 1
``````

Why does reflection of an object in the mirror appear to have the same distance from the mirror as the object is from the mirror?

``````a. because the object is in front of the mirror

-->  b. because the angle of incidence is always the same as the angle of reflection on a flat mirror

c. because the mirror reflects the all lights that shine on it

d. because the reflection is the same size of the object
``````

Identify the reflective rays

``````-->  a. W

b. T

c. K

d. D
``````