3. The negative sign indicates that the image is virtual or the image is behind the mirror. Determine (a) The image distance (b) the magnification of image, 1/di = 1/f – 1/do = 1/5 – 1/10 = 2/10 – 1/10 = 1/10. The magnification of the image (M) : M = di/do = 30 cm / 60 cm = 1/2 times. The plus sign indicates that the image is upright. Wanted : if the object distance (do) = 7 cm then the image distance is …, 1/f = 1/do + 1/di = 1/6 + 1/12 = 2/12 + 1/12 = 3/12. α + (90 - r) + (90 - i') = 180 ° d) i + r = 34 + 34 = 68 °. 1. Substitute r" by 90 + α - i to obtain Mirrors can be plane (flat), concave (curved in), or convex (curved out). Image is virtual or real? i is the angle made by the incident ray and the normal to the interface and is called the angle of incidence. eval(ez_write_tag([[336,280],'problemsphysics_com-large-mobile-banner-1','ezslot_6',700,'0','0'])); b) angle of reflection r = i = 34 ° (by the law of reflection) c) q = 90 - r = 90 - 34 = 56 °. d) Let the angle made by the light ray and the axis of the two mirror system be α instead of 25 °. We first complete the given diagram with the angles of incidence and reflection as shown below and also labeling the incident and reflected rays. di = 60/2 cm = 30 cm. Upright or inverted? If the focal length of a concave mirror is 60 cm, what is the radius of curvature? 3. The focal length (f) of the concave mirror is 4 cm, therefore the patient’s teeth should be less than 4 cm in front of a concave mirror. Optical instrument human eye problems and solutions, Optical instrument contact lenses problems and solutions, Optical instrument magnifying glass problems and solutions, Optical instrument microscope – problems and solutions, Optical instrument telescopes problems and solutions, Force of gravity and gravitational field – problems and solutions, Parabolic motion, work and kinetic energy, linear momentum, linear and angular motion – problems and solutions, Transverse waves – problems and solutions, Speed of the mechanical waves – problems and solutions, Simple harmonic motion – problems and solutions. So the image properties are real, inverted, enlarged. In triangle AOB, we have 14d-Modern FR practice problems-ANSWERS.doc .. Solution: Image enlarged ? tan(i') = tan( 90 - α) = cot (α) = AC / d (a) Write two rules of the new Cartesian sign conventions for spherical mirrors. The size of the image produced by a convex mirror is always smaller than the size of the object, therefore, the mirror is a concave mirror. 6. a) Find the angle of incidence. 13d-Waves and Optics FR practice problems-ANSWERS.doc. AC = 4 tan(75°) = 15 cm The mirror used is a concave mirror or a convex mirror? The focal length of the concave mirror is positive or real because the light passes through the focal point of the mirror. d) Find the angle made by the incident and reflected rays. Simplify to obtain the angle of incidence i' at C In triangle CBE, we have The magnification of the image, according to the image below. The minus sign indicates that the image is inverted. An object vibrates with a frequency of 5 Hz to rightward and leftward. Also r = i (law of reflection). (2) The angle of incidence and the angle of reflection have the same size. α + 90 + i' + r" = 180 ° The focal length is 5 cm. The angle of incidence i = 90 - α = r = i' The distance between the patient’s teeth and the mirror. Example 4: Let AD and CE be the normals to mirror(1) at A and C respectively. α = r + i' = i + i' = 90 ° The tension force of the rope is... 1. Science Class 12 Physics (India) Ray optics and optical instruments Reflection of light by spherical mirrors Reflection of light by spherical mirrors Practice: Spherical mirrors questions The focal length (f) = r/2 = 20/2 = 10 cm. Whhat is the image distance if the object is moved from the original position 1 cm away from the mirror. The focal length of the concave mirror (f) = 15 cm, 1/di = 1/f – 1/do = 1/15 – 1/10 = 2/30 – 3/30 = -1/30. r = i (law of reflection) Substitute ∠CBE by r" We use the diagram shown below to answer the questions. Solution: α + 90 + i' + 90 + α - i = 180 ° If α = 90 °, the incident ray at A and the reflected ray at B are parallel. c) If the distance between the two mirrors id d = 4 cm and the length L of the two mirror system is 3 meters, approximately how many reflections take place between the two mirrors? α + 90 + r' = 180 ° All rights reserved. 2. An image an by a concave mirror is 4 times greater than the object. Solution: (adsbygoogle = window.adsbygoogle || []).push({}); Example 3: Conversely a concave mirror can produce an upright image if the object distance (d) is smaller than the focal length (f). Light waves reflect off of mirrors to form images. For the incident ray at A and the reflected ray at B to be parallel, angles i + r and i' + r' have to be supplementary. Modern Physics MC. Hence i' = r = i = 75 ° What is the focal length of this mirror? If the object is placed 20 cm in front of the mirror then determine the properties of the image. (1) The incident light ray, the reflected light ray and the normal to the interface at the point of incidence make a plane called the plane of incidence If the object is placed 6 cm from a concave mirror, the image distance is 12 cm as shown in figure below. Calculate the image distance (s’): The image distance signed positive means that the image is real because it is passed by light. The ray makes an angle of 25° with the axis of the two mirrors. r" = 90 + α - i number of reflections = N = L / AC = L / d cot(α) 2. © problemsphysics.com. The surface separating the two media is called the interface or boundary. Advertisement Diagram shown below. An image an by a concave mirror is 4 times greater than the object. The image is 0.5 smaller than the object. 14b-Modern FR practice problems.doc. object is placed 6 cm from a concave mirror, the image distance is 12 cm as shown in figure below. We first look at the vocabulary used to describe the reflection of light.