- #1

shawonna23

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From using the mirror equation, i came up with an answer of 1.82m but when i submitted it for webassign, it was wrong. Is the answer supposed to be negative? Please Help!

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- Thread starter shawonna23
- Start date

- #1

shawonna23

- 146

- 0

From using the mirror equation, i came up with an answer of 1.82m but when i submitted it for webassign, it was wrong. Is the answer supposed to be negative? Please Help!

- #2

marlon

- 3,777

- 11

I think this will provide your answer automatically.

Spherical Mirrors

May i give you a piece of advice here ?

When studying mirrors you should make a little list for yourself in which you make four columns and three row. Each row denotes the mirror type (plane, concave, convex) and the columns are like this:

1) mirror type

2) object location (inside or outside the focal point)

3) image (three sub-columns :location, type, orientation of the image with respect to the object)

4) the signs (four sub-columns where you write the signs of f,r,i,m for each row)

f : focal point

r: radius of spherical mirror

i : image distance

m: magnification

pbject distance

Nr 4 will eliminate the chance of you making any mistakes when filling in the parameters of the spherical mirror formula [tex]\frac{1}{p} + \frac{1}{i} = \frac{1}{f}[/tex]

You can do the same for lenses.

If you want a check just let me know and i will verify your tables :)

regards

marlon

Spherical Mirrors

May i give you a piece of advice here ?

When studying mirrors you should make a little list for yourself in which you make four columns and three row. Each row denotes the mirror type (plane, concave, convex) and the columns are like this:

1) mirror type

2) object location (inside or outside the focal point)

3) image (three sub-columns :location, type, orientation of the image with respect to the object)

4) the signs (four sub-columns where you write the signs of f,r,i,m for each row)

f : focal point

r: radius of spherical mirror

i : image distance

m: magnification

pbject distance

Nr 4 will eliminate the chance of you making any mistakes when filling in the parameters of the spherical mirror formula [tex]\frac{1}{p} + \frac{1}{i} = \frac{1}{f}[/tex]

You can do the same for lenses.

If you want a check just let me know and i will verify your tables :)

regards

marlon

Last edited:

- #3

Doc Al

Mentor

- 45,450

- 1,911

Just to add to marlon's post: Often the most confusing thing about using the mirror (and lens) equation is getting the sign convention straight. To add to the confusion, there are several different sign conventions.shawonna23 said:From using the mirror equation, i came up with an answer of 1.82m but when i submitted it for webassign, it was wrong. Is the answer supposed to be negative? Please Help!

With one standard sign convention,

The mirror equation will tell you this, assuming you have the signs of object distance (positive for real objects, like a person) and focal length (negative for diverging mirrors, like convex mirrors). I suspect you made an error with one (or both) of these.

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