Refln
Refln
Refln
Name:
Light Reflection
Read from Lesson 1 of the Reflection chapter at The Physics Classroom:
http://www.physicsclassroom.com/Class/refln/u13l1a.html
http://www.physicsclassroom.com/Class/refln/u13l1b.html
http://www.physicsclassroom.com/Class/refln/u13l1c.html
MOP Connection:
1.
Place a letter in the blank in order to classify the following objects as being either luminous (L) or
illuminated (I) objects.
Sun
Moon
Person
Whiteboard
2.
3.
Light bulb
Candle
These diagrams are intended to represent the path of light from an object to an eye as the eye sights
at the image of the object. Each diagram is incorrect. Discuss what makes them incorrect.
a.
b.
Discussion:
Discussion:
Consider the diagram at the right in answering the next three questions.
4. The angle of incidence is denoted by angle ____.
5. The angle of reflection is denoted by angle ____.
6.
If an incident ray of light makes an angle of 35 with the mirror surface then the
angle of reflection is _______.
7.
Why do windows of distant houses appear to reflect the sun only when rising or setting? Explain in
words. Use the diagram to help, drawing appropriate light rays on the diagram.
Page 1
8.
Use the law of reflection and the embedded protractor in order to draw the reflected ray associated
with the given incident ray for the following plane mirror situations. (Markings are provided at 15
increments.)
9.
10. Now write in your own words a personal definition of what you believe an image of an object is:
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Name:
1.
Describe the difference between diffuse reflection and regular (or specular) reflection.
2.
3.
4.
True or False:
When a beam of light undergoes diffuse reflection, individual rays within the beam do
NOT follow the law of reflection.
Explain your answer.
5.
For each of the five surfaces given below, draw normal lines.
6.
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7.
Identify whether the following phenomenon are attributable to diffuse reflection (DR) or regular
reflection (RR):
a.
The image of a mountain can be clearly seen in the calm waters of a lake. _______
b.
A lacquered tabletop produces a glare of the lamp bulb in the overhead light. _______
c.
Water is sprayed onto a sheet of paper. A laser beam is directed towards the paper, reflects
and produces a red dot on the ceiling. _______
d.
Light from the overhead lights strikes your body and reflects towards all your classmate's eyes.
_______
8.
9.
A microscopic view
of a sheet of paper.
10. Driving at night offers a great example of diffuse vs. regular reflection. A dry road is a diffuse
reflector, while a wet road is not. On the diagrams below, sketch the reflected light off a wet and dry
surface.
Why would the wet road appear to the driver to be darker than the dry road?
11. The diagram below contrasts the reflection of light off a smooth surface (left) with the reflection of
light off a rough surface (right). Compare the two diagrams and explain why the reflected rays for a
rough surface do not result in the formation of an image.
Page 4
Name:
1.
An object (denoted by a dark circle) is placed in front of a plane mirror as shown below. Light from
the object emanates in a variety of directions. For each light ray incident to the mirror, accurately
draw the corresponding reflected ray. Use a protractor, straightedge, and the law of reflection.
2.
For each reflected ray drawn in the diagram above, use dashed lines to trace the reflected ray
backwards behind the mirror. If done correctly, all reflected rays should intersect at the same
location; this location corresponds to the image location.
3.
Make measurements on the diagram to compare the object distance (distance from the object to the
mirror) to the image distance (distance from the intersection point or image location to the mirror).
Record the results of your comparison in the space below.
Page 5
4.
5.
Which of the following statements are true of plane mirror images? List all that apply in
alphabetical order with no spaces between letters.
a. The location of an image is different for different observers.
b. Observers at different locations will sight along different lines at the same image.
c. Every image is located on the mirror surface and at the same location for different observers.
d. Every image is located on the mirror surface, but at a different location for different observers.
e. All observers (regardless of their location) will sight at the same image location.
6.
The diagram below depicts the path of four incident rays emerging from an object and approaching
a mirror. Five lettered locations are shown on the opposite side of the mirror. Which location is
representative of the image location?
7.
The diagram below depicts the path of four reflected rays that originated at the object on the left side
of the mirror and have subsequently reflected from the mirror. Five lettered locations are shown on
the right side of the mirror. Which location is representative of the image location?
Page 6
Name:
Ray Diagrams
Read from Lesson 2 of the Reflection chapter at The Physics Classroom:
http://www.physicsclassroom.com/Class/refln/u13l2d.html
MOP Connection:
ii.
Pick one extreme on the image of the object and draw the reflected ray that will travel to the eye
as the eye sights at this point.
iii.
Draw the incident ray for light traveling from the corresponding extreme on the object to the
mirror.
iv.
Repeat steps ii and iii for all other extremities on the object.
Locating Images
1.
Locate all of the images for the following objects (labeled "o") as produced by the mirror (labeled
"m"). Consider steps 1 and 2 above.
Page 7
4.
5.
Extend this reflected ray beyond the mirror using a dashed line to show that the eye is sighting
along a line directly at A'.
6.
The light which follows the path shown by the reflected ray originated from point A. Show this by
accurately drawing the incident ray that starts at point A and approaches the mirror. Be sure to use
a solid line and put an arrow upon the ray.
7.
Repeat steps #4-#6 in order to show how light travels from point B to the mirror and reflects
towards the eye as the eye sights along a line at B'.
8.
On the diagram, label the point on the mirror where the incident ray from A reflects from the mirror
with the letter "x".
9.
On the diagram, label the point on the mirror where the incident ray from B reflects from the mirror
with the letter "y".
10. Points "x" and "y" represent the points on the mirror which would be needed to view point A and
point B on the object. Where will any other ray from the object reflect from the mirror before
traveling to the eye?
11. What parts of the mirror could be removed without interfering with the eye's ability to see the entire
image of the arrow? Circle these sections of the mirror.
12. For the following objects, (a) draw the corresponding images, and (b) draw and label the incident and
reflected rays that would allow the eye to view the object in the mirror (labeled "m").
Page 8
Name:
13. Front row students Al, Bo, Cy, Di, Ed and Fred are
looking into a 4-foot long mirror that the teacher
strategically placed on the demonstration table.
Their positions are shown in the diagram below. In
the diagram, locate their images and complete the
given statements.
Al can see...
Di can see...
Bo can see...
Ed can see...
Cy can see...
14. The teacher asked the six students to assume different positions in the room. Their positions are
shown below. Determine and label the image locations and complete the given statements.
Al can see...
Di can see...
Bo can see...
Ed can see...
Cy can see...
Page 9
15. Consider the mirror and the stick-person shown in the two diagrams below. The distance between
the mirror and the person is different in the two diagrams. For each diagram, accurately draw and
label the image of the stick-person in the appropriate position. Finally, draw lines of sight from the
eyes of the stick-person to the mirror in order to indicate which portion of the mirror is needed to
view the image. Use a ruler/straight-edge and be precise.
16. Compare the height of the stick-person to the length of mirror needed to view the stick-person.
Make some measurements (from the diagram above) and record below.
17. Does the distance from the stick-person to the mirror seem to affect the amount of mirror that the
person needs to view the image? ________ Explain and support your answer using numerical
values taken from question #15 above.
Page 10
Name:
The diagram below depicts a concave mirror with its principal axis and its center of curvature (C). Five
incident rays are shown traveling parallel to the principal axis.
1. Construct normal lines for each of the five incident rays. (Geometry Review: A line which passes
through the center of a circle will be perpendicular to the circle at its point of intersection. Thus, the
normal line for each of these incident rays passes through C.)
2. Measure the angle of incidence and use the law of reflection to construct five reflected rays at the
appropriate angle of reflection.
3. Construct two more incident rays parallel to the principal axis that strike points 6 and 7. Draw the
normal line and use the law of reflection to draw the corresponding reflected rays.
4.
5.
Propose your personal definition of the focal point: The focal point is ...
6.
Make some generalized statements about rays 1-5 and about rays 6-7. How are they similar and
how are they different?
Page 11
The diagram below depicts a convex mirror with its principal axis and its center of curvature (C). Five
incident rays moving parallel to the principal axis are shown.
7.
8.
9.
As on the front side, construct normal lines for each of the five incident rays. (Geometry Review: A
line which passes through the center of a circle will be perpendicular to the circle at its point of
intersection. Thus, the normal line for each of these incident rays passes through C.)
Measure the angle of incidence and use the law of reflection to construct five reflected rays at the
appropriate angle of reflection.
For each reflected ray, construct extensions of the rays backwards behind the mirror until they
intersect the principal axis.
10. Make some generalized statements about rays 1-5 to describe how they reflect.
Conclusion:
Propose a rule of reflection for both concave and convex mirrors that would describe how incident rays
parallel to the principal axis would behave upon reflection.
Page 12
Name:
Spherical Mirrors
Read from Lesson 3 of the Reflection chapter at The Physics Classroom:
http://www.physicsclassroom.com/Class/refln/u13l3a.html
http://www.physicsclassroom.com/Class/refln/u13l3b.html
http://www.physicsclassroom.com/Class/refln/u13l3c.html
MOP Connection:
1.
2.
3.
4.
The diagrams below show three incident rays. For each diagram, draw the three corresponding
reflected rays on the diagrams. Place arrowheads upon all your rays. (Study the ray diagrams in
your textbook carefully to answer these questions.)
Page 13
5.
State the three rules which describe the predictable reflection of three rays of incident light for a
concave mirror. (See question #4.)
6.
Light from a distant star is collected by a concave mirror. How far from the mirror do the light rays
converge if the radius of curvature of the mirror is 150 cm?
7.
Suppose your teacher gives you a concave mirror and asks you to find the focal point. Describe the
procedure you would use to do this.
8.
9.
Page 14
Name:
Description of Image:
Location:
O: Upright or Inverted
S: Magnified or Reduced
T: Real or Virtual
Description of Image:
Location:
O: Upright or Inverted
S: Magnified or Reduced
T: Real or Virtual
Page 15
Case 3: If the object is located between the center of curvature and the focal point.
Description of Image:
Location:
O: Upright or Inverted
S: Magnified or Reduced
T: Real or Virtual
No Description Required
Case 5: If the object is located between the focal point and the mirror.
Description of Image:
Location:
O: Upright or Inverted
S: Magnified or Reduced
T: Real or Virtual
Page 16
Name:
Description of Image:
Location:
O: Upright or Inverted
S: Magnified or Reduced
T: Real or Virtual
Description of Image:
Location:
O: Upright or Inverted
S: Magnified or Reduced
T: Real or Virtual
Page 17
Use the mirror equation and the magnification ratio to solve the following problems. PSYW
1. Bobby places a 4.25-cm tall light bulb a distance of 36.2 cm from a concave mirror. If the mirror has
a focal length of 19.2 cm, then what is the image height and image distance?
2.
Van Itee, quite concerned about the pimple on his chin, is looking into a concave mirror with a focal
length of 33.6 cm. Determine the image height and image distance of the 2.50-mm sized pimple
when placed 25.2 cm from the mirror.
3.
Al Wayscurious is intrigued by the reflective abilities of his family's soup ladle. The ladle acts as a
concave mirror with a 2.59-cm focal length. Determine the image size of Al's 24.8-cm tall face when
placed 12.8 cm from the ladle's surface.
4.
Mr. H splurged when he bought his Yugo and ordered the side mirror option. The mirror has a
focal length of -88.4 cm. What is the image height of a 4.59-meter tall truck when located 12.6 meters
away from the mirror?
5.
A Christmas tree ornament with an 8.64-cm diameter serves as a convex mirror surface. Determine
the image size and the image distance of a 4-foot tall child standing a distance of 2.65 meters away.
Page 18
Name:
Object-Image Relations
Read from Lesson 3 of the Reflection chapter at The Physics Classroom:
http://www.physicsclassroom.com/Class/refln/u13l3d.html
http://www.physicsclassroom.com/Class/refln/u13l3e.html
MOP Connection:
1.
A 10.0-cm tall object is placed in front of a concave mirror with a focal length of 20.0 cm. For each
object distance, calculate the image distance, magnification, and image height. Sketch a ray diagram
showing the object in the appropriate location and the image with the proper location, orientation
and relative size.
do
a.
50 cm
b.
40 cm
c.
30 cm
d.
20 cm
e.
10 cm
di
Mag.
hi
Page 19
2.
Arrows numbered 1-8 represent object locations for a concave mirror. For each of these objects, use
your understanding of image characteristics to determine the corresponding image location,
orientation and relative size. Since these diagrams have not been created to scale, do NOT use ray
diagrams to determine your answers.
Object
3.
Image
Object
Image
Arrows numbered 1-4 represent object locations for a convex mirror. For each of these objects, use
your understanding of image characteristics to determine the corresponding image location,
orientation and relative size. Since these diagrams have not been created to scale, do NOT use ray
diagrams to determine your answers.
Object
Image
Object
Image
Page 20