Optics of lenses and mirrors question:

In summary, the chart is used as a reference to determine the location of the focal point, and in this case, the object is 24 cm away from the focal point (F).
  • #1
e-me
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So I was going through the playlist of videos here, and have understood everything so far. However, they are going through this question and he introduces this chart, so the student can use it as a reference to know if he got the answer correct.

http://www.freelance-teacher.com/fri17apr_problems.pdf

http://www.youtube.com/watch?v=4154MDNV5ps&feature=relmfu

What I did not understand is, how did he know 24cm lines up with F (within the focal point) as opposed to 2F?

Have I missed a key piece of information?
 
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  • #2
The key piece of information you need to understand the chart is that the distance from the object to the focal point of the lens is twice the focal length (2F). Since the question states that the object is 24 cm away, and the focal length is 12 cm, this means that the distance from the object to the focal point is 24 cm, which lines up with F on the chart.
 

1. What is the difference between a convex and concave lens?

A convex lens is thicker in the middle and thinner at the edges, causing light to converge and form an image. A concave lens is thinner in the middle and thicker at the edges, causing light to diverge and spread out.

2. How does the focal length of a lens affect the image formed?

The focal length of a lens determines the distance at which the image is formed. A shorter focal length results in a wider field of view and a smaller, magnified image. A longer focal length results in a narrower field of view and a larger, less magnified image.

3. What is the difference between a real and virtual image?

A real image is formed when light rays actually converge at a specific point and can be projected onto a screen. A virtual image is formed when light rays appear to converge at a point, but do not actually do so and cannot be projected onto a screen.

4. How does the shape of a mirror affect the image formed?

The shape of a mirror determines how light is reflected and therefore affects the size and orientation of the image. A plane mirror reflects light in all directions and creates a virtual image that is the same size and orientation as the object. A concave mirror reflects light towards a focal point, creating a magnified and inverted image. A convex mirror reflects light away from a focal point, creating a smaller and upright image.

5. What is the difference between reflection and refraction?

Reflection occurs when light bounces off a surface and changes direction without entering the material. Refraction occurs when light passes through a material and changes direction due to a change in speed. Both reflection and refraction can occur with lenses and mirrors, but their effects on light are different.

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