Part | Lab 10: Reflection and Refraction of Light Experiment |: Snell's Law Acrylic rhombus with ray undergoing refraction. Angle of incidence @ Angle of refraction @ N rhombus 72.5 57 Average index refraction Accepted index of refraction 1.5 % difference Find the percent differences. Tablel f=100 mm Questions: 1. Is the image formed by the lens erect or inverted? 2. Is the image real or virtual? How do you know? 3. Explain why, for a given screen-object distance, there are two positions image is in focus. 4. Why is the magnification negative? Il Solve for the focal length. f= If you look at the label near the base of your lens, it gives you its focal lengthin m example, +20mm means 20mm focal length converging lens. A negative focal len; a diverging lens. How well does this number compare with your resultsin 3? Wh be different? 1 1 VS, FOCAL LENGTH BY PLOTTING Z VS d i a. Onthe optical bench, position the lens between a light source (the object) an Be sure the object and the screen are at least 0.80 meter apart. b. Move the lens to a position where an image of the object is formed on the scr Measure the image distance and the object distance. The image distance is tt from the screen to the center of the lens. The object distance is the distance light source to the corner of the lens. Record all measurements in table 3.1. c. Measure the object size (on the screen of the light source) and the image size position of the lens. d. Move the lens to a second position where the image is in focus (do not move or light source). Measure the image distance and the object distance. e. Measure the image size for this position also. f. Move the screen toward the object until you can no longer find two positions where the image will focus. Then move the screen a few centimeters further the object. Repeat parts b and d for this position of the screen and for 4 othe intermediate positions of the screen. This will give you 6 sets of data points (: 12 data points). g. Plot i Vs. ai using the 12 data points. This will give astraight line and the x-a 1 intercepts are equal to //f. Be sure that your axis range goes all the way dow Solve for the focal length. f= if you look at the label near the base of yourlens, it gives you its focal length in mm, for example, +20mm means 20mm focal length converging lens. A negative focal length means a diverging lens. How well does this number compare with your results in3? Why might it be different? FOCAL LENGTH BY PLOTTING -": vs. 'l' a. On the optical bench, position the lens between a light source (the object) and a screen. Be sure the object and the screen are at least 0.80 meter apart. b. Move the lens to a position where an image of the object is formed on the screen. Measure the image distance and the object distance. The image distance is the distance from the screen to the center of the lens. The object distance is the distance from the light source to the comer of the lens. Record all measurements in table 3.1. . Measure the object size (on the screen of the light source) and the image size for this position of the lens. d. NMove the lens to a second position where the image isin focus (do not move the screen or light source). Measure the image distance and the object distance. e. Measure the image size for this position also. f. Move the screen toward the object until you can no longer find two positions of the lens where the image will focus. Then move the screen a few centimeters further away from the object. Repeat parts b and d for this position of the screen and for 4 other intermed ate positions of the screen. This will give you 6 sets of data points (a total of 12 data points). 1 g intercepts are equaltol/f. Be sure thatyour axis range goes all the way down tozero or this will not work. g Plotdivs. using the 12 data points. This will give a straight line and the x-andy- h. Find the percent difference between the two values of the focal length found from the intercepts. Then average these two values and find the percent difference between this average and the focal length found in Part L | L Part I Lab 8: Thin Lenses Experiment 1: Focal Length of a Thin Lens Purpose: To determine the focal length of a thin lens. Equipment: Bench, convex lens, light source (object), screen. 1 1 Theory: For a thin lens: = = + T~ f d, dq Where fis focal length, d,, is the distance between the object and thelens, and d; is the distan the image and the lens. See Figure 3.1. Figure 3.1 Procedure: I. FOCAL LENGTH USING AN OBJECT AT INFINITY