Concave mirror reflection, problems with drawing setup

In summary, the reflection of light in a concave mirror involves the convergence of parallel rays to a focal point, creating distinct image characteristics based on the object's position relative to the focal point and mirror surface. Common problems in drawing setups include incorrect placement of the object or focal point, misrepresentation of ray paths, and failure to accurately depict image characteristics such as size and orientation. Proper understanding of these concepts is crucial for accurate representation and problem-solving in optics.
  • #1
radish
3
0
Homework Statement
I had a homework where a concave mirror with a focal point of -4 centimeters had an object away from it by 5 centimeters (1 cm after the focal point). I decided to solve the problem by drawing it this time and not by using the equations and its giving me a different answer than the equations.
Relevant Equations
1/f=1/Di+1/Do
f= focal point
Di= distance of image
Do= distance of object
1/f = 1/Di + 1/Do
1/Di = 1/f - 1/Do
1/Di = 1/4 - 1/5
1/Di = 1/20
Di = 20 cm
In my drawing i had a focal point of 4 so a center of circumference of 8 and I had an object with a height of 1 cm placed 1 cm after the focal point, so 5 cm, away from the mirror. The distance of the image that i could measure was about 17.3 cm. Am i doing anything wrong?
 
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  • #2
Can you attach your drawing?
 
  • #3
Gordianus said:
Can you attach your drawing?
alright sure.
the closest line to the mirror is the point of convergence, the second line is the object, my lines pass by the focal point and the center of circumference. the point of convergence where the two lines going from the object meet is about 17.3 cm even tho its supposed to be 20cm. thank you for answering.
 

Attachments

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  • #4
My eyes are too old and I can't see the mirror, the optical axis, the focal point and so on. Can you post a better drawing?
 
  • #5
Hope this helps.
IMG-5115.jpg
 
  • #6
radish said:
Homework Statement: I had a homework where a concave mirror with a focal point of -4 centimeters had an object away from it by 5 centimeters (1 cm after the focal point). I decided to solve the problem ...

Am i doing anything wrong

Difficult to say if you don't give us the complete problem statement. What is it asking for ?
And you also don't tell us what you are doing: what is CC ?and what is the text (in arabic?)
1698138976437.png
doing in the picture ?

[edit] :welcome: !

https://www.physicsforums.com/threads/homework-help-guidelines-for-students-and-helpers.686781/

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FAQ: Concave mirror reflection, problems with drawing setup

How do I locate the focal point of a concave mirror?

The focal point of a concave mirror is located at a distance equal to half the radius of curvature (R) from the mirror along the principal axis. This point is called the focal length (f), and it can be found using the formula f = R/2. To locate it practically, you can use a distant light source: the point where the reflected rays converge is the focal point.

What is the correct way to draw ray diagrams for concave mirrors?

To draw ray diagrams for concave mirrors, follow these steps:1. Draw the principal axis.2. Draw the concave mirror as a curved line with its reflective side facing the object.3. Mark the focal point (F) and the center of curvature (C).4. Draw at least two rays from the top of the object: a. A ray parallel to the principal axis that reflects through the focal point. b. A ray passing through the focal point that reflects parallel to the principal axis. c. Optionally, a ray passing through the center of curvature that reflects back along the same path.5. The point where these rays intersect after reflection gives the position of the image.

Why do my reflected rays not converge correctly in my ray diagram?

Incorrect convergence of reflected rays often results from inaccuracies in drawing. Ensure that:1. The rays are drawn straight and accurately.2. The focal point and center of curvature are correctly positioned.3. The laws of reflection (angle of incidence equals angle of reflection) are followed.Double-check measurements and use a ruler for precision.

How do I determine whether the image formed is real or virtual?

An image formed by a concave mirror is real if the reflected rays actually converge at a point. This happens when the object is placed beyond the focal point. A real image can be projected onto a screen. Conversely, if the object is placed between the focal point and the mirror, the reflected rays diverge, and the image formed is virtual. A virtual image cannot be projected onto a screen and appears behind the mirror.

What are common mistakes to avoid when drawing ray diagrams for concave mirrors?

Common mistakes include:1. Incorrectly placing the focal point and center of curvature.2. Not drawing rays accurately parallel or through the focal point.3. Failing to apply the reflection rules correctly.4. Misjudging the scale of the diagram, leading to inaccurate ray paths.5. Not extending the reflected rays far enough to locate the image intersection point.Always double-check your setup and use proper tools for accuracy.

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