The focal length of a mirror is the distance to the focal point, which is the point midway between the geometric center or vertex of the mirror and the center of curvature of the mirror. c. The two lines intersect at a point behind the mirror which is the top of the image. First let’s define some of the variables Our two light rays behave as follows: The image distance must first be determined with this equation before the image magnification can be determined. g. M is the magnification of the mirror Basically they track the path of two light rays as they pass through specific points and are reflected from the face of the mirror. 2/3=0.6.. i.e m is smaller than 1, hence is diminished and is positive and hence the image is virtual. In a concave mirror, the magnification is the ratio of the height of the image to the height of the object. f. D1 is the distance of the reflection from the face of the mirror A plain flat mirror would be rated at 1X and one that makes an object 3 times larger would be rated at 3X. 2) Ray diagrams are a useful way to help understand how these laws work in magnifying mirrors. Study the following equation, called the "mirror equation," which relates the distance of an object (D object), the distance of the image (D image) and the focal length (F) of the mirror: 1/D object + 1/D image = I/F. 2) Magnifying mirrors are rated for their power of magnification based on how much bigger they make an object look. The power in which the seen image is amplified comes in many strengths, but the ideal for routine and daily care is 7 – 10x. Q. 5) Because its surface is harder and not as easily damaged a glass mirror will provide longer life than a plastic mirror and most metal mirrors. 2) Magnifying mirrors are rated for their power of magnification based on how much bigger they make an object look. M=hi/ho=2/3. The magnification of a spherical mirror image can be determined, analytically, if either the focal length or center of curvature of the mirror is known. a. R is the radius of the curved surface of the glass The bottom of the image is a point on the axis directly below the top of the image. b. Note the distance ratio is the same as the height ratio. Copyright 2020 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. Because it’s on the back side of the mirror where you can’t actually see it it’s called a virtual image, 3) So let’s look at a ray diagram. Therefore the type of mirror … Merry has an extensive background in chemical and metallurgical research, physics, nuclear radiation analysis, and associated technologies. For make‐up and shaving mirrors the most common ratings are 3X, 5X, 7X and 10X. The Physics Classroom: Concave Mirrors, The Mirror Equation. 2) The complex explanation is that there is a lot of physics and math behind the magnification. 4) A poorer quality mirror may show some distortion or waviness that will affect its usefulness. For glass mirrors use a soft, damp cloth and, if necessary a little mild detergent or glass cleaner (like Windex). b. Ray 2 originates at the focal point, passes through the top of the object and is reflected back parallel to the axis of curvature – but we perceive it as passing through the glass in line with this reflection. It is the ratio of the height of the image to the height of the object and is denoted as m. The magnification, mproduced by a spherical mirror can be expressed as: Here, h is the height of image and h’is the height of the object. Only convex mirrors can form virtual and diminished image. Hence, the expression for magnification (m) becomes: m = h’/h = -v/u. Substitute the required information into the mirror equation, as follows: 1/4 + 1/D image = 1/6; 1/D image = 1/6 – 1/4 = - (1/12); D image = - 12. For make‐up and shaving mirrors the most common ratings are 3X, 5X, 7X and 10X. 3) For most users a 3X or a 5X mirror works very well. What will be the distance of the object, when a concave mirror produces an image of magnification m? 1) The amount of magnification is determined by two factors; How do you find the image distance and magnification? When choosing a mirror, check the quality of the reflection and then decide if the magnification meets your needs. In a pocket size compact or other small diameter mirror a 10X magnifier works but in a larger mirror the image becomes less useful as you look further away from the center of the reflection. Note that its large magnitude helps spread out the reflected energy. When objects are beyond the focal point of the mirror, the images seen are real images, but they are inverted. The curvature of the glass – for any given mirror this is a fixed number and doesn’t change. For this reason, concave mirrors are classed as spherical mirrors. The mirror must be a spherical mirror (concave mirror) as the magnification in plane mirror is never -1 but always 1. Perhaps if the user’s vision is declining a bit or if they are doing very detailed work a 7X mirror would be appropriate. 1) The simple explanation is that because the curvature of the mirror reflects light at an angle the reflected image is magnified. 1) Mirrors function according to the laws of physics – in this case the laws of reflection. How do magnifying mirrors work – the easy stuff? For plastic or other mirror materials refer to the manufacturer’s directions. Second Formula for Magnification There is another formula of magnification Note : - If magnification (m) is positive , It means image formed is virtual and erect If magnification (m) is negative, It means image formed is real and inverted Questions Example 10.1 - A convex mirror … How do magnifying mirrors work – the technical stuff. Ans.convex mirror. As the object is always above the principal axis, the height of the object is always positive. He is an avid amateur astronomer, accomplished chess player, and a health and fitness enthusiast. The formula for magnification is = height of image / height of object = -1. a. Ray 1 originates at the center of curvature, passes through the top of the object and is reflected back through the center of curvature – but we perceive it as passing on through the glass in a straight line. For make‐up and shaving mirrors … A virtual mirror image is an image from which rays of reflected light appear to diverge. A plain flat mirror would be rated at 1X and one that makes an object 3 times larger would be rated at 3X. When objects are positioned between the focal point of a concave mirror and the mirror's surface, or the vertex, the images seen are “virtual”, upright and magnified. A plain flat mirror would be rated at 1X and one that makes an object 3 times larger would be rated at 3X. i. H1 and D1 need to be calculated and once we know them there’s a simple equation for M. Next let’s look at the equations for this mirror. The image is upright and three times larger than the object. When objects are positioned between the focal point of a concave mirror and the mirror's … b. F is the focal distance of the mirror – it is 1/2 of the radius of curvature Michael holds a Bachelor of Technology from Ryerson University. Also convex mirror always produces images smaller than the size of the object so it's magnification is always less than 1. There is a formula for the magnification but, unfortunately, it is not always applied correctly. The distance of the user from the mirror, which, of course, is variable. Magnification is also equal to the ratio of image distance to the object distance. Remember that some of the finishes on other parts of the mirror are not as damage resistant as glass and treat them accordingly. The negative sign remains in the result only if the image turns out to be inverted, instead of upright. The magnification is also equal to the negative of the ratio of the distance of the image from the mirror … c. H0 is the height of the object we’re reflecting A magnifying mirror, otherwise known as a concave mirror, is a reflecting surface that constitutes a segment of the inner surface of a sphere. h. R, F, H0 D0 are either known or can be fairly easily measured Bu… ©2019, Baci Mirrors. Skipping the details for the moment – up to a point, the further away the user gets from the mirror the larger the image. Jerdon Tri-Fold Two-Sided Lighted Makeup Mirror. Once you have a mirror follow the manufacturer’s instructions for cleaning and maintaining it. A magnifying mirror, otherwise known as a concave mirror, is a reflecting surface that constitutes a segment of the inner surface of a sphere. As a demonstration of the effectiveness of the mirror equation and magnification equation, consider the following example problem and its solution.