Optics and Ray Diagrams lab
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School
Nassau Community College *
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Course
101
Subject
Astronomy
Date
Dec 6, 2023
Type
Pages
7
Uploaded by leyahdhall75
Optics and Ray Diagrams Ray Diagrams Before you start your ray diagrams, watch the following video that I have made explaining how to do a ray diagram. You should also print out the note from blackboard on Ray Diagrams (under the Lab Notes heading). This has all the definitions that I will describe on the video. How to do a Ray Diagram:
https://youtu.be/jA6DSa7Doa0
For the following two problems, you will be creating a ray diagram for a lens with the following characteristics: f = 3 cm diameter = 8 cm Object height (h
o
) = 3 cm Problem 1: Object distance = 12 cm Problem 2: Object distance = 8 cm For the next two ray diagrams, you will be creating a ray diagram for a lens with the following characteristics: f = 5 cm diameter = 8 cm Object height (h
o
) = 3 cm
Problem 3: Object distance = 12 cm Problem 4: Object distance = 3 cm Some of you may need help to complete problem 4, I have recorded the following video to help you with this so just click the following link. How to do a Ray Diagram for a Virtual Image:
https://youtu.be/5TN1sRotyCU
We have two types of images that can be created by a lens, a real image and a virtual image. A real image is an image that can be projected onto a screen. A real image is almost always on the opposite side of the lens and inverted when compared to the object. A virtual image is an image that appears to come from a point but is not actually there. This image almost always on the same side of the lens and erect when compared to the object. Using the images formed by your ray diagrams fill the information asked for in the following table. Problem Real or Virtual Inverted or Erect Image Size (cm) Magnification = h
i
/h
o
1 2 3 4 Questions 1) What is the relationship between the object distance from the lens and the image size?
2) What is the relationship between the focal length of the lens and the image size? Ray Diagrams of Telescopes
Figure #1: This figure shows the ray diagram of a telescope made with two lenses. Use figure #1 and the following information to the to answer questions. The object is 10 cm from the objective lens and is 3 cm in height. The focal length of the objective lens is 5 cm and is labeled as F
1
in the figure. The image the objective produces is 2.7 cm in height. The image of the objective lens is the object for the eyepiece (this is the same as if we placed an object at this point). The eyepiece has a focal length of 3 cm and the image it produces is 8.5 cm in height. 3) What type of image is produced by the objective? By this I mean real and inverted, or virtual and erect.
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4) What type of image is produced by the eyepiece? 5) What type of image is produced by the telescope? 6) Using the equation for magnification in the previous section, calculate the magnification of the objective lens. 7) Calculate the magnification of the eyepiece? 8) Knowing that the image seen through the eyepiece is the image of the telescope, calculate the magnification of the telescope. 9) According to theory, if we multiply the magnification of the objective by the magnification of the eyepiece we should get the magnification of the telescope. Do this calculation to prove that this is true. Optics We have two types of lenses a convex or converging lens and a concave or diverging lens. These two lenses can be seen in Figure #2.
Figure #2 ray diagrams of a converging and a diverging lens. A converging lens takes light that enters it and bends or refracts the light so that they will meet at a single point. If the light that enters the lens is infinitely far away that point is called the focal length. A diverging lens takes light rays that enter it and spreads them out. If you extend the rays that exit the lens backwards, they will meet at a single point in front of the lens as seen in figure 2. These two images are of two converging lenses. The one on the left has a focal length of 10 cm; the one on the right has a focal length of 20 cm. In both images, the object is placed 30 cm away from the lens.
10) What is the relationship between the brightness of the image and the focal length of the lens? These two images show a 10 cm focal converging lens. The photo on the right shows the image resulting from the lens with its full aperture. The image on the left shows the same lens, but with an image formed using a 3 cm aperture. 11) What is the relationship between image brightness and the aperture of the lens? If we were to build a telescope with two converging lenses, the magnification is given by: 𝑀 =
𝑓
???𝑒?𝑡?𝑣𝑒
𝑓
𝑒𝑦𝑒??𝑒?𝑒
We have four lenses: Lens Focal Length (cm) A 4 B 3.5 C 10 D 3
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Calculate the magnification of the following combinations of lenses: Objective Eyepiece Magnification C A C B C D From your answers in the table, what is the relationship between the focal length of an eyepiece and the magnification of a telescope?