# Where is the image formed and what is its magnification?

• suf7
In summary, the object is placed 10cm in front of a convex lens with a focal length of 20cm. The image is formed at a distance of 20cm from the lens and has a magnification of -2. An accurately drawn ray diagram would show an inverted image.
suf7
Need Help With Lens!

An object is placed 10cm in front of a convex lens of focal length 20cm. Where is the image formed and what is its magnification??..Your solution should include an accurately drawn ray diagram?

Pleeez help me with this question?...im so stuck??

Thanks.

Use the lens formula:

1/f = 1/u + 1/v

where f = focus, u = object distance from lens, and v = image distance from lens

So:

1/20 = 1/10 + 1/v

Solve for v
v = -20cm

So the image is located at 20cm

Last edited:
suf7 said:
An object is placed 10cm in front of a convex lens of focal length 20cm. Where is the image formed and what is its magnification??..Your solution should include an accurately drawn ray diagram?

Pleeez help me with this question?...im so stuck??

Thanks.

You should have at least[/b] be able to know where to start! The lens equation would have been a good one. If you didn't even know this, then you should review the material again and know what that equation is for, and how to use it.

If you do that, then you would have been able to derive what IntuitioN did, AND, be able to decipher what the "v = -20 cm" answer means (i.e. what does the NEGATIVE sign signifies). So look at the lens equation, and understand how each symbol are defined.

Zz.

IntuitioN said:
Use the lens formula:

1/f = 1/u + 1/v

where f = focus, u = object distance from lens, and v = image distance from lens

So:

1/20 = 1/10 + 1/v

Solve for v
v = -20cm

So the image is located at 20cm

oh right, thank you...so when i work out the magnification would it be 20/10 which is 2?

And for your ray diagram draw the lens with a compass. Then put in the object and draw the rays.

the ray diagram should have given you a clue to the image's location, magnification, and orientation. it is actually pretty easy.

magnification formula is $$m = - \frac{d_{i}}{d_{o}}$$
where di is the image distance and do is the object distance and the negative sign means that if it was positive then the image is in the same direction as the object, if neaitve then the opposite direction.
thi DIRECTION means that if the object were an arrow poiting upward, then a negatie magniification would mean that the image arrow would point downwwward, signifying an inverted image

## 1. Where is the image formed?

The image is formed at the point where the light rays intersect after passing through a lens or reflecting off a mirror. This point is called the focal point.

## 2. What affects the location of the image?

The location of the image is affected by the curvature and refractive index of the lens or the angle of reflection for a mirror. It is also influenced by the distance between the object and the lens or mirror.

## 3. How is the magnification of an image determined?

The magnification of an image is determined by the ratio of the size of the image to the size of the actual object. It can be calculated by dividing the height or width of the image by the height or width of the object.

## 4. What does a positive magnification value indicate?

A positive magnification value indicates that the image is upright and larger than the object. This is typically seen in convex lenses and concave mirrors.

## 5. How does a negative magnification value differ?

A negative magnification value indicates that the image is inverted and smaller than the object. This is commonly observed in concave lenses and convex mirrors.

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