What is the length of Joe's image in the mirror?

In summary, Joe, who is 1.6 meters tall, enters a room with a large convex mirror with a radius of curvature of 30 meters. He is initially 5 meters away from the mirror but doesn't see it until he turns around and startles himself. When he falls forward, the length of his image changes and the normal magnification equation cannot be used. By using the equation twice for his feet and head, the distance from head to toe of Joe's image is calculated to be 0.98 meters.
  • #1
jcvince17
41
0

Homework Statement



A guy named Joe, who is 1.6 meters tall, enters a room in which someone has placed a large convex mirror with radius of curvature equal to 30 meters. The mirror has been cut in half, so that the axis of the mirror is at ground level. As Joe enters the room, he is 5 meters in front of the mirror, but he is looking the other way, so he fails to see it. When he turns around, he is startled by his own image in the mirror. ( i calculated 8.75m for this answer and its correct.)
NOW:
Joe is so startled by his image that he falls forward. (Assume that his feet stay at the same position.)

Now what is the length (i.e., the distance from head to toe) of Joe's image


Homework Equations



1/f = 1/s' + 1/s

m = y'/y = s'/s

The Attempt at a Solution



f = 15m

I calculated 1.2 and got this as a reply to my wrong answer:
This was Joe's height when standing. Since he has fallen, his length is now parallel to the axis of the mirror instead of perpendicular. Therefore, the normal magnification equation does not apply. See the hint for help

I now have two chances left for a correct answer. I do not know what I am doing wrong. I am sure I am just not thinking of something simple again.

please help.

here is picture:
101033B.jpg

 
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  • #2
Hi jcvince17!
jcvince17 said:
1/f = 1/s' + 1/s

Just use that equation twice: once for his feet, and once for his head. :wink:
 
  • #3
tiny-tim said:
Hi jcvince17!


Just use that equation twice: once for his feet, and once for his head. :wink:


doing so i get:

1/-15 = 1/s' + 1/3.4
s' (head) = -2.77

1/-15 = 1/s' + 1/5
s' (feet) = -3.75

so i subtract these two numbers and have an answer of 0.98 m

Thank You!
 
Last edited:

Related to What is the length of Joe's image in the mirror?

What is the relationship between object size and image size in a mirror?

The size of an object and its image in a mirror are directly proportional. This means that as the object gets closer to the mirror, its image gets larger, and as the object moves away from the mirror, its image gets smaller.

Why does my reflection in a concave mirror appear distorted?

A concave mirror is curved inward, causing light rays to converge and create a magnified or distorted image. This distortion is due to the mirror's shape and the way it reflects light.

How does the distance between an object and a mirror affect the size of its image?

The distance between an object and a mirror affects the size of its image because the farther away the object is from the mirror, the smaller its image will appear. This is due to the principle of light reflection and the way light rays behave when they hit a surface.

Can the size of an image in a mirror be larger than the actual object?

Yes, it is possible for the size of an image in a mirror to be larger than the actual object. This occurs when the object is placed between the focal point and the mirror's surface, resulting in a virtual, magnified image.

How is the size of an image in a mirror affected by the curvature of the mirror?

The curvature of a mirror affects the size of an image by altering the angle at which light rays reflect off the mirror's surface. A concave mirror will produce a larger image, while a convex mirror will produce a smaller image due to the way they bend and reflect light.

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