Draw Ray Diagram for Converging Lens w/ 25cm Focal Length

The ray diagram shows that the virtual image is on the same side as the object, giving the appearance of the object being larger and located 37.5cm in front of the lens. In summary, a converging lens with a focal length of 25cm produces a virtual image that is 2.50 times larger than the object and located 37.5cm in front of the lens.
  • #1
lilkrazyrae
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A converging lens has a focal length of 25cm. A 1.00cm tall object is placed 15.0cm in front of the lens. Find the image location and size, and describe it. Draw a ray diagram.

Ok so I get 1/p + 1/q = 1/f rearranged for q=pf/p-f which equals -37.5, so the object is 37.5cm behind the lens. and then m=-q/p=2.50cm. The h'=mh(i)=2.50*1.00=2.50cm tall. This all works out

BUT the ray diagram doesn't make the image at 37.5cm behind the lens. Some one help please!

Sorry to double post but I thought maybe someone here could help me!
 
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  • #2
lilkrazyrae said:
A converging lens has a focal length of 25cm. A 1.00cm tall object is placed 15.0cm in front of the lens. Find the image location and size, and describe it. Draw a ray diagram.

Ok so I get 1/p + 1/q = 1/f rearranged for q=pf/p-f which equals -37.5, so the object is 37.5cm behind the lens. and then m=-q/p=2.50cm. The h'=mh(i)=2.50*1.00=2.50cm tall. This all works out

BUT the ray diagram doesn't make the image at 37.5cm behind the lens. Some one help please!
The - sign means that the image is not behind the lens. When the object is inside the focal length you get a virtual image. A virtual image appears to be an image on the same side as the object.

The rays through the lens do not converge on the other side. Project the rays back in front of the lens. They will converge on the virtual image which you can see by looking back through the lens toward the object.

AM
 

1. How do you draw a ray diagram for a converging lens with a 25cm focal length?

To draw a ray diagram for a converging lens with a 25cm focal length, follow these steps:

  • Draw the principal axis, which is a straight line passing through the center of the lens.
  • Mark the focal point on the principal axis, which is 25cm away from the lens.
  • Draw a ray parallel to the principal axis and passing through the center of the lens.
  • Draw a ray passing through the focal point and then through the lens, refracting towards the principal axis.
  • The point at which these two rays intersect after refraction is the image of the object placed in front of the lens.
  • Draw a third ray passing through the center of the lens without changing direction. This ray will also intersect at the image point.

2. What is the significance of the focal length in a ray diagram?

The focal length is the distance between the center of the lens and the focal point. It determines the amount of light that is bent or refracted by the lens. In a ray diagram, the focal length helps to determine the position and size of the image formed by the lens.

3. How does the position of the object affect the ray diagram for a converging lens?

The position of the object affects the ray diagram for a converging lens in two ways. Firstly, the distance of the object from the lens determines the height of the object's image. Secondly, the position of the object relative to the focal point determines whether the image will be real or virtual.

4. Can a converging lens with a 25cm focal length form both real and virtual images?

Yes, a converging lens with a 25cm focal length can form both real and virtual images. If the object is placed beyond the focal point, the image formed will be real and inverted. If the object is placed between the lens and the focal point, the image formed will be virtual and upright.

5. What is the purpose of a ray diagram for a converging lens?

The purpose of a ray diagram for a converging lens is to determine the position, size, and nature of the image formed by the lens. It also helps to understand the behavior of light as it passes through the lens and is refracted. Ray diagrams are useful in predicting the properties of images formed by different types of lenses and can be used to design and improve lens systems.

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