How does the presence of water affect the image formed by a converging lens?

In summary, the conversation discusses the placement of a needle and a converging lens in a beaker, with the needle being illuminated and an image formed on a screen. When the beaker is filled with water, the image changes and the screen is moved to get a new sharp image. The conversation also touches on the use of the lens maker's formula and the apparent depth of the needle in relation to the lens. The summary concludes with the solution of the apparent depth being 22.5cm from the lens, with the reminder that the real depth should not include the air.
  • #1
apunisheriii

Homework Statement


A needle of length 5.0cm placed at the bottom of a beaker and a converging lens of focal length 20.0cm is held 30.0cm from the needle.The needle is illuminated with a lamp from the bottom.An image of the needle is formed on a screen.The beaker is now filled with water(refractive index=4/3)to a depth of 20cm.What change can be observed in the image?
If the screen is moved to get a new sharp image,what will the image distance and object be in this new position??

i squeezed my brain so hard..still don hv any idea at all..becoz there's a space (air)between the lens and the water.When i am using the lens maker's formula,im confusing whether i should assume there r three lens -water,converging lens and water or two or one..
can somebody give some hints about how to solve it??
 
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  • #2
Forget about the lens for a moment. From the viewpoint of someone looking down into the beaker (from the position of the lens), will the addition of the water make the apparent position of the needle closer or farther away? By how much?
 
  • #3
oh!
the apparent depth is 22.5cm from the lens
and let u=22.5cm and solve it by lens formula
is it correct??
 
  • #4
sorry...
mistake...real depth shouldn't include the air...u=25cm
by the way!thnx!
 
  • #5
apunisheriii said:
the apparent depth is 22.5cm from the lens
How did you get that value? Realize that the water is only 20 cm deep.
 
  • #6
apunisheriii said:
sorry...
mistake...real depth shouldn't include the air...u=25cm
by the way!thnx!
Now you've got it. :smile:
 

FAQ: How does the presence of water affect the image formed by a converging lens?

What is geometrical optics?

Geometrical optics is a branch of physics that studies the behavior of light using the principles of geometric optics, which assumes that light travels in straight lines and can be represented by rays. It focuses on the study of light as it passes through different media and interacts with various surfaces and objects.

What are the basic elements of geometrical optics?

The basic elements of geometrical optics include light sources, objects, and optical instruments such as mirrors, lenses, and prisms. These elements are used to manipulate and control the path of light in order to form images or project light onto a surface.

What is the difference between reflection and refraction in geometrical optics?

Reflection occurs when light bounces off a surface, while refraction is the bending of light as it passes through a medium with a different refractive index. In geometrical optics, reflection is used in mirrors to form images, while refraction is used in lenses to focus light.

What is the principle of least time in geometrical optics?

The principle of least time states that light always takes the path that requires the least amount of time to travel from one point to another. This principle is used to explain the behavior of light as it travels through different media and interacts with different surfaces and objects.

How is geometrical optics used in everyday life?

Geometrical optics has many practical applications in everyday life, such as in the design of eyeglasses, cameras, and telescopes. It is also used in the study of vision and the human eye, as well as in the development of laser technology and fiber optics for communication systems.

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