# Focal length of a concave mirror

• hds29ka
In summary, the conversation was about an experiment in which the focal length of a concave mirror was measured. The method involved collecting a light globe, paper/screen, and concave mirror, and taking 5 trials of object and image distances. The results were then used to find the focal length using either a graphical method with a calculator or the equation 1/f=1/v+1/u. The conversation also included questions about the two methods and their accuracy.
hds29ka

## Homework Statement

Focal length of a concave mirror.
This was an experiment, done in class.

I was required to collect a light globe:(of course with a power source) for the object, paper:screen/image, and a concave mirror.

I created the images, of the globe filament, to the screen, and measured.

I took 5 trials of V and U, where; U=Object distance, and V= Image distance. The results were; 1.)V=25.0, U=38.0
2.)V=22,0, U=47.0
3.)V=20.0, U=57.5
4.)V=18.5, U=75.0
5.)V=18.0, U=88.5

From here, I could use the graphics calculator (1/v for y-axis, and 1/u for x-axis), or 1/f=1/v+1/u for each and average them.

Question 1.: What is the graphical method (calculator.)?
Question 2.: What is the Mirror equn method?
Question 3.: Why is the graphical method more accurate, than 1/f=1/v+1/u?

1/f=1/v+1/u

## The Attempt at a Solution

1.) stat, 1/u for list1, 1/v for list2, GRPH, GPH1, X, Copy, Menu, GRAPH,
Y=-1.0522075X+0.067, Enter, G solv, Xcal- when Y=0, Ycal- when X=0.

Then f=1/yintercept and f=1/xintercept for focal length.

2.) average values (of 1/f=1/v+1/u).

What conclusions did you draw? Is there a particular question you wish to ask?

What do you mean when you say
hds29ka said:
Then f=1/yintercept and f=1/xintercept for focal length.
??

## 1. What is the focal length of a concave mirror?

The focal length of a concave mirror is the distance from the center of the mirror to the point where all parallel rays of light converge after reflection. It is represented by the symbol "f" and is measured in meters.

## 2. How is the focal length of a concave mirror calculated?

The focal length of a concave mirror can be calculated using the formula "f = R/2", where R is the radius of curvature of the mirror. This formula is applicable for all concave mirrors, regardless of their size or shape.

## 3. Does the focal length of a concave mirror change with the distance of the object?

Yes, the focal length of a concave mirror changes with the distance of the object. When the object is placed farther away from the mirror, the focal length increases. Conversely, when the object is closer to the mirror, the focal length decreases.

## 4. How does the focal length of a concave mirror affect the image formed?

The focal length of a concave mirror determines the size and position of the image formed. When the object is placed beyond the focal length, the image is real, inverted, and smaller in size. If the object is placed between the focal point and the mirror, the image is virtual, upright, and larger in size.

## 5. Can the focal length of a concave mirror be negative?

Yes, the focal length of a concave mirror can be negative. This happens when the object is placed between the mirror and the focal point, resulting in a virtual image. In this case, the focal length is represented by a negative value to indicate that the image is formed on the same side as the object.

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