How do I find the radius of curvature?

In summary, the conversation discusses the focal distance, radius of curvature, and the relationship between the two. It is mentioned that the focal length is half of the radius of curvature and the image is virtual. The value of q is also mentioned, with the correct value being -127.55 cm. The conversation also includes a correction of a previous calculation error.
  • #1
Hawking Jr
5
0
Homework Statement
A concave makeup mirror is designed so that a person 29.3 in front of it sees an upright image at a distance of 54.2 cm behind the mirror.What is the radius of curvature of the mirror?
Relevant Equations
1/f=1/p + 1/q and 1/p +1/q = 2/R
I figured out that the focal distance is 19.01868
 
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  • #2
And you want to know what? The radius of curvature? Do you know the relationship between the focal length and the radius of curvature?

And by the way, is the image real or virtual? And how did your answer to that question affect the way you did your calculation?
 
  • #3
The focal length is half of the radius curvature. So I multiplied it by 2 and I still got it wrong. The image is virtual.
 
  • #4
Hawking Jr said:
The image is virtual.

Correct. So what is the value of ##q##?
 
  • #5
I think it is 54.2 cm
 
  • #6
No. ##q## is negative when the image is virtual!
 
  • #7
Oh! Give me a moment to do it over.
 
  • #8
Okay I redid the problem and the answer I have now is 127.55 cm. Is it correct?
 

Related to How do I find the radius of curvature?

1. How do I calculate the radius of curvature?

To calculate the radius of curvature, you can use the formula: R = (1 + (dy/dx)^2)^(3/2) / |d^2y/dx^2|, where dy/dx is the first derivative of the curve and d^2y/dx^2 is the second derivative of the curve. Alternatively, you can also use the formula: R = |(y-y0)/dy/dx|, where y0 is the y-coordinate of the center of curvature.

2. What is the importance of knowing the radius of curvature?

The radius of curvature is an important parameter in understanding the shape and behavior of curves. It is used in various fields such as engineering, physics, and mathematics to analyze and design curved structures, predict the trajectory of moving objects, and calculate the focal length of curved mirrors and lenses.

3. Can the radius of curvature be negative?

Yes, the radius of curvature can be negative. This indicates that the curve is concave downwards. It is common for curves to have different radii of curvature at different points along its length, and these radii can be positive or negative depending on the shape of the curve.

4. How do I find the radius of curvature of a circle?

The radius of curvature of a circle is equal to its radius, as all points on the circle have the same curvature. Therefore, to find the radius of curvature of a circle, simply measure the radius of the circle using a ruler or compass.

5. Can the radius of curvature be infinite?

Yes, the radius of curvature can be infinite. This occurs when the curve is a straight line, as a straight line has a constant slope and no curvature. In this case, the formula for finding the radius of curvature would result in a division by zero, indicating an infinite radius of curvature.

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