How Does Light Behave When Emitted From a Focal Point Through a Convex Lens?

In summary, The bulb is placed at one focal point of a convex lens. Five rays can be drawn from the bulb, with the bulb located on the optical axis. The rays will go in different directions and can be collected by the lens to ignite a piece of paper. The direction of light rays is reversible, so if the direction of the sunrays is turned over, they will follow the same path back towards the sun. When starting rays from the focus, they will go in the direction of the bulb after crossing the lens.
  • #1
choco_moo
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Homework Statement


1. A small bulb is placed in front of a convex lens. It is placed at one focal point of the lens. Draw at least five rays from the bulb that pass through the lens.

Where is the lens located in this case? Explain. (Hint: How are the rays that have passed through the lens oriented? From where do these rays appear to have come?)


Homework Equations


none


The Attempt at a Solution


Sorry I can't show the picture but since the bulb is at the focal point, doesn't that mean it is right on the optical axis? I really don't know how to draw 5 rays from that.
 
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  • #2
It's on the axis. The rays begin at the lamp and go in different directions.
 
  • #3
Yes, the bulb is on the optical axis. So just draw a lens with its optical axis and focal points and put the bulb at one of them. Consider the bulb a point-like light source.

Remember that you can collect the sun rays with a convex lens, and ignite a piece of paper. The rays of sun come from so far that they are parallel. Rays incident parallel with the optical axis are collected in the focus at the other side of the lens. Draw 5 such rays.

You know that the direction of light rays is reversible. If you turn the direction of the sunrays over, they will follow the same path as they arrived, going back towards the sun.

Starting rays from the focus, in what direction will they go after crossing the lens?


ehild
 
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1. What is a convex lens?

A convex lens is a type of optical lens that is thicker at the center and thinner at the edges, causing light rays to converge and form a single focal point. It is commonly used in cameras, telescopes, and eyeglasses to magnify and focus images.

2. How does a convex lens work?

A convex lens works by bending light as it passes through the lens, causing the rays to converge at a focal point. This bending of light is known as refraction, and it occurs due to the curved shape of the lens. The amount of bending depends on the curvature and thickness of the lens.

3. What are the uses of convex lenses?

Convex lenses have a wide range of uses in various fields. They are commonly used in optics and photography to magnify and focus images, in magnifying glasses and microscopes for better visualization, and in corrective lenses for people with nearsightedness or farsightedness. They are also used in scientific instruments such as telescopes and binoculars.

4. How are convex lenses different from concave lenses?

Convex lenses and concave lenses have opposite shapes and properties. A convex lens is thicker in the middle and thinner at the edges, while a concave lens is thinner in the middle and thicker at the edges. Additionally, a convex lens bends light rays towards a focal point, while a concave lens spreads them out.

5. What is the relationship between convex lenses and xrays?

Xrays are a form of electromagnetic radiation that can pass through objects, including convex lenses. However, xrays cannot be focused or magnified by convex lenses, as they are not affected by refraction. Convex lenses can only be used to focus and magnify visible light, not xrays.

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