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Reflection of Light |
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It is the phenomenon of change in the path of light without any change in medium. |
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Spherical Mirrors |
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It is a part of a hollow sphere, whose one side is reflecting and other side is opaque. |
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Sign Conventions and Rules for Drawing Ray Diagrams |
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These new cartesian sign conventions adopted during measurements. |
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Relation between Focal Length and Radius of Curvature in Spherical Mirrors |
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Consider a ray of light AB, parallel to the principal axis, incident on a spherical mirror at point B. The normal to the surface at point B is CB and CP = CB = R, is the radius of curvature. |
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Mirror Formula |
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A formula giving the relation between focal length of the mirror, object distance, image distance and radius of curvature. |
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Linear Magnification of Spherical Mirror |
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Linear magnification is ratio of the size of the image to the size of the object. |
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Applications of Spherical Mirrors |
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A convex mirror is used as a rear view mirror in vehicles as images are small, erect. This gives us a wider view of the traffic behind. |
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Refraction of Light |
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Light not only bounces off surface it goes through some of them often slowing down and changing direction in the process called refraction. It occurs at the point where light travels from one medium to another of different density. Refraction produces mirages and rainbows. |
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Relation between Relative Refractive Index and Absolute Refractive Index |
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Let light travel from air to medium 1. If c and v1 are the velocities of light in these media, the refractive index of medium 1 with respect to air, or the absolute refractive index of medium 1. |
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Total Internal Reflection and its Application |
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A ray of light incident normally to XY goes undeviated along AB. As the angle of incidence increases, the angle of refraction also increases. |
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Spherical Refracting Surface |
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A refracting surface, which forms a part of a sphere of transparent refracting material, is called spherical refracting surface. The two types are convex spherical refracting surfaces and concave spherical refracting surfaces. |
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Lenses |
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Lens is a portion of transparent refracting medium bound by two spherical surfaces or one spherical surface and the other plane surface. |
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Lens Formula |
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This gives the relation between focal length, object distance and image distance from the optical centre of the lens. |
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Lens Maker's Formula |
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It is a relation that connects focal length of a lens to radii of curvature of the two surfaces of the lens and refractive index of the material of the lens. |
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Ray diagrams for convex lens showing the formation and nature of image for different positions of the object |
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Convex Lens : Object at Infinity, Object Beyond 2F. |
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Thin Lenses Placed in Contact |
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Let two thin lenses L1 and L2 of focal lengths f1 and f2 be placed in contact so as to have a common principal axis. It is required to find the effective focal length of this combination. Let O be a point object on the principal axis. |
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Power of a Lens |
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Ability of the lens to converge a beam of light falling on the lens. |
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Prism |
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A prism is a portion of a transparent medium bounded by two plane faces inclined to each other at a suitable angle. |
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Dispersion of Light |
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It is the phenomenon of splitting of a beam of white light into its constituent colors on passing through prism. The order of colors from the lower end are violet, indigo, blue, green, yellow, orange and red. |
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Applications of Prism |
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An optical instrument, which is used for observing pure spectra of sources of light in the laboratory. |
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Spectra |
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When light emitted from a source is examined directly in a spectroscope, we observe the emission spectrum of the source. |
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Scattering of Light |
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When light passes through a substance or gas, a part of it is absorbed and the rest scattered away. The basic process in scattering is absorption of light by the molecules followed by re-radiation in different directions. |
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Human Eye |
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One of the most complicated optical devices is the human eye. Let us see the construction of the human eye and then the mechanism of image formation. |
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Camera |
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A photographic camera consists of a converging lens system at least one end of a box and a light sensitive film at the other end, a focusing device for adjusting the distance of the lens from the film and an exposure arrangement which provides the correct exposure. |
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Simple Microscope or Magnifying Lens |
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It consists of a converging lens of small focal length. By keeping the object close to the lens, a virtual, erect and magnified image is obtained. |
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Compound Microscope |
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It is an optical instrument used for observing highly magnified images of tiny objects. |
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Astronomical Telescope |
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An instrument used for observing distinct images of heavenly bodies. In the normal adjustment, the final image is formed at infinity. |
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Reflecting Telescope |
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The objective lens is replaced by a concave parabolic mirror of large aperture. The images in such telescopes are brighter and have a high resolving power compared to astronomical telescope. |
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Wave Optics - Introduction |
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The branch of physics dealing with the study of optical phenomena is called optics. This can be divided into two categories, ray optics and wave optics. |
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Wavefront |
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Wavefront is the continuous locus of all the particles of a medium that are vibrating in the same phase. A light source sends out disturbance (waves) in all the directions. |
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Huygen's Wave Theory |
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Huygen proposed a hypothesis for the geometrical construction of the position of a common wavefront at any instant during the propagations of waves in a medium. |
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Verification of Laws of Reflection on the basis of Huygen's Wave Theory |
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Consider AB a plane incident wavefront on a mirror
M1M2. Let ÐBAA' =
Ði = be the angle of incidence. Every point on the wavefront AB is a source of secondary disturbance. |
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Verification of Laws of Refraction based on Huygen's Wave Theory |
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XY is a plane surface separating a denser medium of refractive index from a rarer medium. |
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Superposition of Interference |
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The two short lined waves traveling in opposite direction first add up (center) to form a resultant wave and then move off as if nothing happened to them. |
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Interference of Light |
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Since light has a very small wavelength, we need two slits, which send out two continuous coherent waves. Since the two slits are placed very close. |
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Coherent Sources |
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In different colors, the fringes have different widths. This indicates that a relation exists between colour and fringe widths. But before going to the relation, let us know more about the condition under which constructive interference or destructive interference occurs. |
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Young's Double Slit Experiment |
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Let A and B be two fine slits, a small distance 'd' apart. Let them be illuminated by a monochromatic light of wavelength l. |
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Diffraction |
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Diffraction in sound waves and radio waves are readings observed as they have a relatively longer wavelength compared to light waves. |
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Resolving Power |
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The ability of the instrument to resolve the images of two point objects lying close to each other. Due to the wave nature of light each point object produces its own diffraction pattern, which overlap, and the image can no longer be identified. |
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Polarization |
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Light is an electromagnetic wave with electric and magnetic field vectors varying sinusoidally, perpendicular to each other as well as perpendicular to the direction of propagation of wave of light. |
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Malu's Law |
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If q is the angle between the plane of transmission of the analyzer and the polarizer, then intensity of the transmitted light I |
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Scattering Due to Polarization |
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When a beam of white light is passed through a medium containing particles of size nearly equal to the wavelength of light, the beam gets scattered. This scattered light is seen in a direction perpendicular to that of incidence and is found to be plane polarized. |
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Applications of Polarized Light |
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Polaroids are used in sun glasses. They reduce the intensity and the glare by cutting down the horizontally polarized light. |
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Doppler Effect in Light |
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Whenever there is a relative motion between a source of light and the observer, the apparent frequency of light received by the observer is different from the true frequency of light emitted actually from the source of light. |
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Summary |
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Ray optics is also called geometrical optics as it uses the geometry of straight-line paths (rays) to explain the optical phenomena. |
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Summary(Contd...) |
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Continuous emission spectrum, which contains all the wavelengths in a particular region. The range of wavelengths emitted depends only on temperature of the source. |
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Numerical - 1 |
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A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15cm. Give the location of the image and the magnification. Describe what happens as the needle is moved farther from the mirror. |
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Numerical - 2 |
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A square wire of side 3.0 cm is placed 25 cm away from a concave mirror of focal length 10 cm. What is the area enclosed by the image of the wire? Given: The centre of the wire is on the axis of the mirror, with its two sides normal to the axis. |
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Numerical - 3 |
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A small pin fixed on a table top is viewed from above from a distance of 50 cm. By what distance would the pin appear to be raised if it is viewed from the same point through a 15 cm thick glass slab held parallel to the table? Refractive index of glass = 1.5. Does the answer depend on the location of the slab? |
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Numerical - 4 |
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A needle placed 45 cm from a lens forms an image on a screen placed 90 cm on the other side of the lens. Identify the type of lens and determine its focal length. What is the size of the image if the size of the needle is 5.0 cm? |
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Numerical - 5 |
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An object of size 3.0 cm is placed 14 cm in front of a concave lens of focal length 21 cm. Describe the image produced by the lens. What happens if the object is moved farther from the lens? |
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Numerical - 6 |
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Double convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces having the same radius of curvature. What is the radius of curvature required if the focal length of the lens is to be 20 cm? |
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Numerical - 7 |
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A glass lens has a focal length of 5 cm in air. What will be its focal length in water? Refractive index of glass is 1.51 and that of water is 1.33. |
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Numerical - 8 |
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A screen is placed 90 cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20 cm. Determine the focal length of the lens. |
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Numerical - 9 |
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For a given source of light, the angle of minimum deviation of a 600 prism is 560. What is its refractive index? |
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Numerical - 10 |
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Numerical - 11 |
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Calculate the angle of dispersion between red and violet colours produced by a filter glass prism of refracting angle of 600. |
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Numerical - 12 |
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Calculate the dispersive power for crown and flint glass. |
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Numerical - 13 |
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Monochromatic light of wavelength 600 nm is incident from air to water. What are the wavelength, frequency and speed of (i) reflected, and (ii) refracted light. Refractive index of water is 1.33. |
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Numerical - 14 |
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In Young's double slit experiment, the two interfering sources are 0.5 nm apart. Using l = 500 nm, interference fringes are observed on a screen distant 1m. What is angular width of fringe? |
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Numerical - 15 |
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Sodium light l = 589 nm is incident on a Young's double slit experiment. The separation between the two slits is 3.0 mm. If the screen is placed at a distance of 4m from the slits, locate the position of the tenth bright fringe on the screen. |
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Numerical - 16 |
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In Young's double slit experiment the slits are separated by 0.5 mm and screen is placed 1.5 m away. The distance between the central bright fringe and the fifth bright fringe is 1.5 cm. What is l? |
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Numerical - 17 |
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In a Young's experiment, the width of the fringes obtained with light of wavelength 6000 nm is 2.0 mm. What will the fringe width be if the entire apparatus is immersed in a liquid of refractive index of 1.33. |
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Numerical - 18 |
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Two coherent sources have intensities in the ratio of 81:1 what is the ratio of maximum intensity to the minimum intensity in the fringe system? |
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Numerical - 19 |
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In Young's double slit experiment what is the intensity at a point on screen where the two waves arrive at a phase difference of (i) 600 (ii) 900 and (iii) 1200? |
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Numerical - 20 |
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In Young's double slit experiment, the intensity at a point is 75% of maximum intensity. What is the smallest distance of this point from the central fringe? Given d = 0.1mm, D = 1m and l = 600 nm. |
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Numerical - 21 |
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A laser operates at 5 x 1014 Hz and has an aperture of 5 x 10-3. What is the angular spread of the beam? |
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Numerical - 22 |
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Red light of l = 650 nm from a distant source falls on a slit of 0.5 mm width. What is the distance between the two dark bands on each side of the central bright band of diffraction pattern observed on screen placed 1.8 m from the slit? |
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Numerical - 23 |
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What is the minimum aperture of the objective of a telescope, which will enable two neighboring stars to be seen separately? The angle subtended by the two stars at the objective of telescope is 3 x 10-6 radian. l= 546 nm. |
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Numerical - 24 |
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In Young's experiment, let the lights of l = 5.4 x 10-7 m and 6.85 x 10-8m be used in turn. Keeping the same geometry, compare the fringe widths in the two cases. |
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Numerical - 25 |
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Two coherent sources of intensity ratio 100:1 interfere. Deduce the ratio of intensity between the maxima and minima in the pattern. |
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Numerical - 26 |
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In Young's double slit experiment, we observe the 10th maximum for l = 1000o A. What will be visible if the source of light is replaced by light of wavelength 5000o A. |
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Numerical - 27 |
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The ratio of the intensities at minima to maxima in the interference pattern is 9:25. What will the ratio of the widths of the two slits be in Young's double slit experiment? |
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Numerical - 28 |
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In a star, hydrogen emits waves of l = 650 nm. The "red-shift" in the wave length is 1.5 nm. What is the speed of the star with respect to Earth? |
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Numerical - 29 |
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Two polarizing sheets are placed with their planes parallel so that light intensity transmitted is maximum. Through what angle will either sheet be turned so that intensity drops to half the maximum value? |
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Numerical - 30 |
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The critical angle of incidence of water for total internal reflection is 480 for a certain wavelength. What is the polarizing angle and the angle of refraction for light on water at this angle? |
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Numerical - 31 |
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A glass plate (m= 1.5) is used as a polarizer. Obtain the polarizing angle of incidence. What is the angle of refraction when the reflected light is plane polarized? |
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Numerical - 32 |
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The spectral line for a given element in the light received from a distant star is shifted towards a longer wavelength by 0.030%. Calculate the velocity of the star in the line of sight. |
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Numerical - 33 |
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A diffraction grating one cm wide has 1000 lines and is used in the third over. What are the diffraction angles for violet and orange lights? What is the angular size of the diffraction maximum for monochromatic light? The wavelengths for violet and orange are 400 nm and 600 nm respectively. |
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Numerical - 34 |
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