By obtaining the real image of a distant object at its focus, the focal length of the concave mirror can be estimated as shown in the diagram. The concave side of a spoon has a focal length of 5 00 cmthe concave side of a spoon has a focal length of 5. Be careful with the sign of the focal length in the lens formula. Materials required a concave mirror, a mirror holder, a small. The polished surface of the concave mirror and the distinct object should be facing each other. Determination of focal length of a converging lens and mirror.
The magnification of the image is given by m i h i d 4 both relations given in eq. We can repeat the experiment with concave mirrors of different focal lengths. The lateral magnification of the mirror or lens is the ratio. Find the focal length of a concave mirror that produces four times larger real image of an object held at 5cm from the mirror. Image formation for mirrors and lenses type focal length f object distance s image distance s character orientation size concave mirror converging lens f 0 s 2f f 2f real inverted enlarged s mirror diverging lens f 0 s concave mirror is 20 cm to the right of the original location of the ball. The same can also be proved by using the mirror formula. Pdf an optical surface of variable concave parabolic shape and a clear aperture of 30 mm was created using two rings to deform a flat 50.
Materials required a concave mirror, a measuring scale, a screen a mirror holder and mirror stand. Get an answer for describe how you find the focal length of a concave mirror. In other words, in the smallangle approximation, the focal length \f\ of a concave spherical mirror is half of its radius of curvature, \r\. A concave spherical mirror has the silvered surface of. A convex mirror can only produce a virtual image since all reflected rays will diverge. Fermats principle concave mirror use fermats principle to determine the shape equation of a concave mirror in air that produces a perfect image of a distant at infinity point source a distance f to the left of the mirror vertex. The focal length of a mirror is basically the distance between the pole of the spherical mirror to the focal point of the mirror. Concave lenses 14 here are some exercises with concave lenses. Determination of focal length of concave mirror and convex. Find the radius of curvature of the concave mirror. Note that if we placed the screen in between the light source and mirror it. Use a light source, concave mirror, and half screen accessory on an optics bench to measure the focal length of the concave mirror. If one uses a concave mirror with a focal length of 2.
Concave mirror problems and solutions solved problems in. Using your data from procedure, part c, calculate the focal length of the concave mirror. Mathematics of curved mirrors lesson notes learning. In case, if the focal length of the given thin convex lens is not known then rough value of its focal length f l should be estimated first to ensure that its focal length is less than that of the concave lens. Procedure fix concave mirror to mirror holder and place it on table. Position the light source so the crossed arrow target is aimed at the concave mirror and the concave surface of the mirror faces the light source. Concave mirrors when a real object is placed on one side of the principal axis of a concave spherical mirror at the center of curvature, a real, inverted image of the same size is formed on the other side of. Light reflection and refraction class 10 important. To determine the focal length of concave mirror practical i to determine focal length of a given concave mirror. What focal length eyepiece is required to give a magnification of 8. Hence the focal point and focal length of a concave mirror are real while the focal point and focal length of a convex mirror arevirtual. Turn the face of mirror towards a distant object a candle in this case. Numericals based on convex and concave mirror gurukul for. To get a well illuminated and distinct image of the distinct object, the distant object should be well illuminated.
Mirror example consider a concave mirror radius r 10 cm then. Concave mirrors when a real object is placed on one side of the principal axis of a concave spherical mirror at the center of curvature, a real, inverted image of the same size is formed on the other side of the principal axis at the center of curvature. The focal lengths of a biconvex lens and a concave mirror are shown in figures 1 and 2, respectively. We begin by calculating the focal length of a concave mirror or, more specifically, the distance from the mirror vertex to the point where a reflected ray from a distant object intersects the optical axis. Focal length of concave mirror and convex lens selfstudys. Measure the focal length from the center of the convex lens to the focal point. Determine the focal length of a convex mirror that produces an image that is 16. A concave mirror of focal length 10 cm and a convex mirror of focal length 15 cm are placed facing each other 40 cm apart. Then, cab and fab are approximately right triangles with the same opposite side ab. To create a real image with a concave mirror, the object must be outside the focal point. Concave and convex mirror questions construct optical.
Focal length and magnification of a concave mirror. Finding the focal length of a concave mirror guided psi physics. To see this clearly we need to remove the screen and lens and place the concave mirror on the optical bench facing the light source and about 300mm away. Use this data to determine an average value of the focal length, f, and the radius of curvature, r of the concave mirror. An object is held at 30cm in front of a convex mirror of focal length 15cm.
As a final example we consider a single concave mirror in combination with an intermediate plane mirror, as shown in fig. Centre of curvature c centre of sphere from which the mirror is made. Place the concave mirror at the other end of the optics bench. Focal length f f is positive for converging and negative for diverging lenses. Record p and q three different relative positions of the object, mirror and image screen. An object is placed i 10 cm, and ii 30 cm from the mirror. Concave mirror problems and solutions solved problems. Spherical mirrors are portions of spheres, one side which is silvered and serves as the reflecting surface.
Should that not be a minus sign on the left hand side. Focal length of a concave mirror lab report conclusion. Describe how you find the focal length of a concave mirror. Use a light source, concave mirror, and halfscreen, all on an optics bench, to measure the focal length of the concave mirror. The object distance is the distance from the object to the mirror or lens. There are two types of curved mirror convex and concave. In this approximation, all rays are paraxial rays, which means that they make a small angle with the optical axis and are at a distance. For writing an excellent lab report sample, you can use the template of an outstanding laboratory report as your guide. Focal length of a c oncave mirror use a light source, concave mirror, and half screen accessory on an optics bench to measure the focal length of the concave mirror. To find the focal length of a convex mirror using a convex lens.
In this approximation, all rays are paraxial rays, which means that they make a small angle with the optical axis and are at a distance much less than the radius of curvature from the optical axis. Chapter 26 geometrical opticschapter 26 geometrical optics. Or should it be a plus sign for mirrors and minus for lenses. The focal length of an optical system is a measure of how strongly the system converges or diverges light. Mathematics of curved mirrors lesson notes learning outcomes.
Using the mirror and magnification equations, determine the image position and its. Principal axis straight line joining the pole to the centre of curvature. Aug 03, 2020 a concave mirror of focal length ft can form a magnified erect as well as an inverted image of an object placed in front of it. By measuring d o and d i the focal length can be determined. At what distance from a concave mirror of focal length 10 cm. The purpose of this activity is to measure the focal length of a concave mirror. Image formation for mirrors and lenses type focal length f object distance s image distance s character orientation size concave mirror converging lens f 0 s 2f f 2f real inverted enlarged s mirror diverging lens f. Solution solving the mirror equation, we have a object distance is larger than focal length f, f5. The selected object should be visible with your naked eyes.
That is, the concave mirror is 20 cm to the right of the original location of the ball. Example 3 a concave mirror with a focal length of 32. Mount the light source at one end of the optics bench. Determination of focal length of concave mirror and convex mirror. Focal length of a concave mirror universal 550 physics experiment manual. Note that in step 2, the rays leaving the lens are diverging and they will not cross. Spherical mirror a mirror with a surface that is either concave or convex.
The final image, like the original object, is approximately one focal length from the tangent plane to m. A concave mirror should be always placed near an open window. Focal length for concave mirror is taken as position and for convex lens is negative. Find the object and image distances, assuming that a the object lies beyond the center of curvature and b the object lies between the focal point and the mirror. Object placed inside focal length of converging lens f. Calculate the position of the images formed by the following concave lenses. Justify this statement stating the position of the object with respect to the mirror in each case for obtaining these images. Focal length of a concave mirror comprehensive 850 physics. The focal length f of a concave mirror is given as a positive value. Pdf development of a variable focal length concave mirror for on.
R 11 and r 2 2 are positive for convex outward surface and negative for concave surface. Concave mirror where in front of a concave mirror should you place an object sothatthe imageisvirtual. Dec 07, 2019 focal length boys method focal length of a concave mirror lab report conclusion. The beam from a point object located off the zaxis is converted to a collimated beam by one side of mirror m and returned to the other side of m by the plane mirror. Use a light source, concave mirror, and half screen accessory on an optics bench. Background concave and convex mirrors are examples of spherical mirrors. There are lots of examples online that might be very practical. The purpose of this activity is to use a light source, concave mirror, and halfscreen, all on an optics bench, to measure the focal length of the concave mirror.
Select a distant object from the laboratory window distance should be more than 50 ft. If the object is placed further from the concave spherical mirror than the focal length, do f, the image is real and upsidedown see fig. Any light ray traveling parallel to the principal axis is reflected by the curved mirror. One mark questions convex mirror for seeing traffic at the. Light reflection and refraction class 10 important questions. Focal length of a concave mirror comprehensive 850. We can approximate the focal length in a spherical mirror to be equal to half of the radius of a. Simulator procedure as performed through the online labs select the focal length using the slider. Focal length f is positive for converging and negative for diverging lenses. If the inner surface is the reflecting surface, the mirror is. The focal length of the convex mirror is positive, whereas that of the concave mirror is negative.
From the figure shown, it can be inferred that the focal length of the special mirror is approximately half of the. Cbse class 10 science lab manual focal length of concave mirror and convex lens experiment 4a aim to determine the focal length of concave mirror by obtaining the image of a distant object. If an object lies in front of the concave mirror, at any point farther from the mirror than the focal point f, then light rays from that object reflect from the mirror surface and form a real image. The distance from the mirror to the focal point is called focal f length f. Image formation for mirrors and lenses type focal length f object distance s image distance s character orientation size concave mirror converging lens f 0 s 2f f 2f real inverted enlarged s mirror diverging lens f 0 s focal length of a convex mirror that produces an image that is 16. The distance between an object and its image is 45. Materials required a concave mirror, a mirror holder, a small screen fixed on a stand, a measuring scale and a distant. Apply the thinlens equation and the mirror equation to determine the focal length of a converging biconvex lens and mirror.
The focal length of the concave mirror is positive or real because the light passes through the focal point of the mirror. Cbse class 10 science lab manual focal length of concave. How far is its centre of curvature i from the pole ii from the focus. Focal length of a concave mirror universal 550 physics. To find focal length of a concave mirror procedure. H splurged when he bought his yugo and ordered the side mirror option. The focal length and the radius of curvature of the mirror are also determined. Spherical mirrors the focal point f of a concave mirror is halfway between the center of curvature of the mirror c and the mirror at b. Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on youtube. This paper describes the spherical concave mirror method for measuring the index.
An object is placed 20 cm from the concave mirror of focal length 10 cm, then image is formed at a behind the mirror b between the mirror and focus c at focus d centre of curvature of mirror ans. Focal point is a point where all the rays become parallel or converge to meet after reflection. A concave mirror, a mirror holder, a white screen fixed on a stand or a white wall, an object candle and a metre scale. The focal point f and focal length f of a positive convex lens, a negative concave lens, a concave mirror, and a convex mirror. Focus focal point f the halfway point between the centre of curvature and the. Determination of the spherical aberration and the focal. Ncert class 10 science focal length of concave mirror and. One characteristic feature of all thin lenses and concave mirrors is the focal length, f, and is defined as the image distance of an object that is positioned infinitely far way. The imaging properties of concave mirrors concave mirrors form images as well as lenses. The same experimental setup can be used to determine the focal length of ideal concave mirrors with negligible errors for an introductory level of geometrical optics. Hence the radius of curvature and the focal length are positive for concave mirrors and negative for convex mirrors. Physics 41 determination of focal length of a converging lens and mirror objective.
Find the image distance for this mirror when object distance is a 25. How far from a concave mirror with a focal length of 30. Biconvex glass lens, spherical concave mirror, meter ruler, optical bench, lens holder, selfilluminated object generally a vertical arrow, screen. A point object is placed between the mirrors, on their common axis and 15 cm from the concave mirror. Magnification, m, is the ratio of image size to object size. One mark questions convex mirror for seeing traffic at.
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