Focal Length of a Concave Mirror using Parallel Rays - Method I Theory
· Determine the focal length of a concave mirror – quickly with a minimum of materials. · For a spherical concave mirror – parallel rays of light focus to a point. The distance from the mirror to the focused point image is the focal length of the mirror. Materials Included: • Economy Optical Bench (Optional) • 10 cm focal length concave mirror Materials Provided by You: · Incandescent Frosted 60 Watt bulb with an F drawn on it (Optional) · A Ruler and a sheet of paper (for focusing screen) · Permanent ink (Sharpie) Pen Procedure: 1. Aim your mirror at a distant light source greater than 6 meters away in a darkened room. You can use the sun outdoors or even inside through a window. 2. Place a sheet of paper (focusing screen) between the mirror and light source so that light can strike the mirror and reflect back to the paper (see diagram below). 3. Move the paper toward and away for the mirror to find the position where the reflected light forms the image of a small spot on the paper. 4. Measure the distance between the mirror and the image on the spot with a ruler 5. Focal Length of Mirror using Method I: ______________ cm Q. While finding out the focal length of a convex lens, Ashok kept it on a stand on the optical bench at 10.5 cm. He adjusted the stand carrying the screen to obtain sharp image of a distant tree on it and finally got it when this stand was at 20.8 cm on the optical bench. The focal length of the lens is – (a) 10.3 cm (b) 10.5 cm (c) 20.8 cm (d) 5.1 cm Q.Ritu obtained a distinct image of a distant tree on the screen with the help of a concave mirror. To find focal length of the mirror she shall have to measure distance between- (a) mirror and the tree (b) screen and the tree (c) mirror and the screen (d) mirror and tree as well as between screen and the tree Q. A teacher obtains distinct image of a distant tree on a screen with the help of a convex lens and then asks her four students A,B,C, D to describe nature and size of image. Answers given by them were (A) virtual, inverted, smaller than object (B) real, inverted, smaller than object (C) virtual, erect, same size as that of object (D) real, erect, same size as that of object Correct answer was given by (a) A (b) B (c) C (d) D Q.Four students A, B, C, D traced the path of a ray of light through a glass slab as shown below. Who has traced the path correctly ? The student who has drawn correct path is. (a) (A) (b) (B) (c) (C) (d) (D) Q.After performing the experiment of tracing path of a ray of light through a glass slab, four students A,B,C, D measured angle of incidence and angle of emergence and worked out the relationship between the two as [A] < i = <e [B] < i < <e [C] < I > <e [D] <i = 1/<e Correct relationship has been obtained by (a) A (b) B (c) C (d) D Q.A teacher set up the stand carrying a convex lens of focal length 15 cm at 20.5 cm on the optical bench. She asked four students A,B,C and D to suggest the position of the screen on the optical bench so that a distinct image of a distant tree is obtained immediately on it. The positions of screen suggested by each of them were as- A ___ at 35.5 cm B ___ at 5.5 cm C ___ at 50.5 cm D ___ at 7.5 cm. Correct position of the screen was suggested by (a) A (b) B (c) C (d) D Q. For determining focal length of a concave mirror, a teacher asks her students to Identify concave mirror from a few mirrors lying on the table. The reason given by A,B,C and D for picking up the right mirror is ___ A ___ the mirror is depressed at the center and self image formed is enlarged and erect. B ___ the mirror is raised at the center and self image formed is smaller and erect C ___ the mirror is plane all over and self image is of same size D ___ the mirror is depressed at the center and self image formed is enlarged and inverted. The correct selection is taken by: (a) A (b) B (c) C (d) D Q.Students performed experiment to determine focal length of a convex lens. by obtaining image of a distant tree on the screen. Their teacher asks four students A,B,C,D to describe nature and size of image. Description given by them is ___ A ___ Image is virtual, smaller and erect B ___ Image is real, smaller and erect C ___ Image is virtual, enlarged and inverted D ___ Image is real, smaller and inverted. The correct selection is taken by: (a) A (b) B (c) C (d) D
1 Comment
27/10/2016 10:56:52 pm
Art deco has its roots in the first half of the twentieth century. It has come back into the popular culture now and deserves consideration as a worthy style of decor for any home.
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