Describe different types of mirrors. An enlarged image of the face helps in having a better shave. What is the value of the radius of curvature and magnification of a plane mirror? The difference between the actual distance between the pole of a mirror optical centre , of a lens and the point object or image and observed distance measured on optical bench is called index error. The image formed was inverted and reduced. For this purpose, indirect method is used, as described below. The relationship of the values of and from Trial 1 and Trial 2 can also be observed in Trial 3 and 4 for both convex lens 1 and 2.
All the six sets of observations may complicate the graph. Also, focal lengths of a convex and a concave lens were determined. Which mirror is used by a surgeon and why? A convex lens has both sides rounded outward causing the light rays to converge towards one another. Fix the lens again in the lens holder on optical bench. One part was done when the lenses were in contact, two lenses placed on the same mount. An image needle I is put behind the convex lens and moved to a position at which there is no parallax between tip of inverted image of O needle and tip of I needle.
In this method the object consists of a pin set vertically in a special carrier or simply stuck in a cork held by a clamp and stand. Move the image-pin I, beyond 2f 1 and remove parallax between the tip of the image of O and the tip of I by moving your eyes to the left and then to the right side of the image and seeing that the two tips remain in contact as you move your eye. A concave lens has both sides rounded outward, causing the light rays to diverge away from one another. The object will now be situated in the focal plane of the lens, i. Fix them together with the help of cellotape at the rim. The tips will get separated. An auxiliary convex lens L is introduced between the convex mirror M and object needle O as shown in ray diagram a.
Experiments to measure the focal length of a converging lens For details of these conventions see pages 273-74. A concave lens has both sides rounded inward, causing the light rays to diverge away from one another. Fix the convex lens in the middle of the optical bench and place one pin on either side of it. Is the focal length of a mirror change i due to change in medium ii or colour of light. Why a convex mirror is used as a driving mirror in automobiles? Graphically and algebraically determining the nature of image formed in a convex, a concave and combined lenses using thin lens equation and ray diagram is the main objective of the experiment.
In the presence of your instructor, place the lens on to the optical bench and observe the clarity of your image. Start from zero on either axes. The experimental value of focal length of the concave lens obtained from Table W3 and W4 are -163. They also play a significant role in optical devices like cameras and projectors. Which type of magnification are you expecting for this image? Biconvex lenses have two outward-curving edges. Apparatus : An optical bench with three upright central upright fixed , two outer uprights with lateral movements , a convex lens with lens holder , two optical needle , one thin , one thick a knitting needle and a half meter scale. The percent deviation of focal length in convex lens 1 is 2.
The distance between pin and lens will then be equal to the focal length of the lens. What is the principal axis of a lens? Apparatus An optical bench with three uprights central upright fixed, two outer uprights with lateral movement , a convex lens with lens holder, two optical needles, one thin, one thick a knitting needle and a half metre scale. No sales to private individuals. If the magnification is more them one enlarged image , mirror is concave. The first image formed is the object for the second convex lens. The straight line passing through the centre of curvature of the curved surfaces of the lens is the principal axis of a lens.
Figure 2: Ray diagram for the combination of two convex lenses not drawn to scale Table W3. Table W4 yielded a more accurate value with respect to the theoretical value of -150 mm. The thin lens equation would still work in this situation. What are paraaxial and marginal rays? Several pairs of values of u and v are found and the results entered in a table as shown. When viewing the ruled screen as described in Part 4. Each member of the group must complete at least one ray diagram. Draw straight lines joining u 1 with v 1; u 2 with v 2; u 3 with v 3;…….
Notice that in Table W3, the two lenses are in contact while in Table W4, the lenses are not in contact with each other. To Find the Focal Length of a Convex Mirror, Using a Convex Lens Aim To find the focal length of a convex mirror, using a convex lens. How will you distinguish between a plane, a concave and a convex mirror, without touching them? If the teacher decides to have the students carry out only one variant, then the determination of the focal length by autocollimation is to be preferred. A mean value for the focal length f may then be calculated. If the magnification is one, mirror is plane. Is chromatic aberration takes place in mirror? The focal length of concave mirror is taken negative, while focal length of convex mirror is taken positive. An inverted and enlarged image of the object needle will be seen.
This is why it is necessary to be familiar with the equation above. Give distinction between real and virtual image. Figure 3: Ray diagram for the concave-convex lens 1 combination not drawn to scale Conclusion This experiment yielded an acceptable experimental values of focal lengths of both concave and convex lenses relative to the theoretical value. What types of mirror are used in search lights and in head lights of the vehicles? A concave mirror of small aperture is used by a surgeon to throw a narrow and sharp beam of light into the eye, nose, ear and throat for medical check up. This is demo video of experiment to find the focal length of convex lens. Once you have a clear image, measure the distance from the lens to the screen. Ray Tracing Diagram for Trial 4 of Convex Lens 2 not drawn to scale Table W2.
The distance between lens and screen now gives the focal length of the lens. The tips will get separated. C Determination of v for different values of u 8. What are the various assumption made in deriving lens formula? The simplest theory works as follows: When you are adding or subtracting two numbers, the error of the result is the sum of the errors. Is mirror formula applicable for a plane mirror? The percent deviation yields to 9. Fix an upright at 50 cm mark and put lens holder and lens in it. For best results, attention should be given to the tilt of the plane mirror so that the tip of the image and the tip of the object pin appear to touch Experiments to measure the focal length of a converging lens at the same level as the centre of the lens.