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(i) A point object is placed in front of a double convex lens (or refractive index `mu=n_2/n_1` with respect to air) with its spherical faces of radii of curvature `R_1 and R_2` Show the path of rays due to refraction at first and subsequently at the second surface to obtain the formation of the real image of the object. Hence, obtain the lens maker's formula for a thin lens. (ii) A double convex lens having both faces of the same radius of curvature has refractive index 1.55. Find out the radius of curvature of the lens required to get the

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Draw a ray diagram showing the formation of the image by a point object on the principal axis of a spherical convex surface separating two media of refractive indices `n_1 and n_2`, when a point source is kept in rarer medium of refractive index `n_1`. Derive the relation between object and image distance in terms of refractive index of the medium and radius of curvature of the surface. Hence, obtain the expression for lens maker's formula in the case of thin convex

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) Draw a ray diagram to show refraction of a ray of monochromatic light passing through a glass prism. Deduce the expression for the refractive index of glass in terms of angle of prism and angle of minimum deviation, (ii) Explain briefly how the phenomenon of total internal reflection is used in fibre

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) Obtain lens maker's formula using the expression`n_2/v-n_1/u=((n_2-n_1))/R`Here, the ray of light propagating from a rarer medium of refractive index `(n_1)` to a denser medium of refractive index `(n_2)` is incident on the convex side of spherical refracting surface of radius of curvature R. (ii) Draw a ray diagram to show that image formation by a concave mirror when the object is kept between its focus and the pole. Using this diagram, derive the magnification formula for the image

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) Figure shows a convex spherical surface with centre of curvature C separating the two media of refractive indices `n_1 and n_2`. Draw a ray diagram showing the formation of the image of a point object O lying on the principal axis. Derive the relationship between the object and image distance in terms of refractive indices of the media and the radius of curvature R of the surface. (ii) Define the magnifying power of a compound microscope. Why should both the objective and the eyepiece have small focal lengths in a

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Trace the rays of light showing the formation of an image due to a point object placed on the axis of a spherical surface separating the two media of refractive indices `n_1 and n_2`. Establish the relation between the distance of the object, the distance of image and the radius of curvature from the central point of the spherical surface. Hence, derive the expression of the lens maker's

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) Draw a ray diagram for formation of image of a point object by a thin double convex lens having radii of curvatures `R_1 and R_2` and hence, derive lens maker's formula. (ii) Define power of a lens and give its SI unit. If a convex lens of length 50 cm is placed in contact coaxially with a concave lens of focal length 20 cm, what is the power of the

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) Draw the ray diagram for the formation of image of an object by a convex mirror and use it (along with the sign convention) to derive the mirror formula. (ii) Use the mirror formula to show that for an object kept between the pole and focus of a concave mirror the image appears to be formed behind the

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) Draw a labelled ray diagram showing the image formation of a distant object by refracting telescope. Deduce the expression for its magnifying power when the final image is formed at infinity. (ii) The sum of focal lengths of the two lenses of a refracting telescope is 105 cm. The focal length of one lens is 20 times that of the other. Determine the total magnification of the telescope when the final image is formed at

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Define magnifying power of a telescope. Write its expression. A small telescope has an objective lens of focal length 150 cm and an eyepiece of focal length 5 cm. If this telescope is used to view a 100 m high tower 3 km away, find the height of the final image when it is formed 25 cm away from the

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How is the working of a telescope different from that of a microscope? The focal lengths of the objective and eyepiece of a microscope are 1.25 cm and 5 cm, respectively. Find the position of the object relative to the objective in order to obtain an angular magnification of 30 in normal

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Draw a ray diagram to show the working of a compound microscope. Deduce an expression for the total magnification when the final image is formed at the near point. In a compound microscope, an object is placed at a distance of 1.5 cm from the objective of focal length 1.25 cm. If the eyepiece has a focal length of 5 cm and the final image is formed at the near point. Estimate the magnifying power of the

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) (a) Draw a labelled ray diagram to show the formation of image in an astronomical telescope for a distant object. (b) Write the three distinct advantages of a reflecting type telescope over a refracting type telescope, (ii) A convex lens of focal length 10 cm is placed coaxially 5 cm away from a concave lens of focal length 10 cm. If an object is placed 30 cm in front of the convex lens. Find the position of the final image formed by the combined

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Draw the labelled ray diagram for the formation of image by an astronomical telescope. Derive the expression for its magnifying power in normal adjustment. Write two basic features which can distinguish between a telescope and a Compound

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) AJse Huygens' geometrical construction to show how a plane wavefront at t = 0 .propagates and produces a wavefront at a later time.(ii) Verify, using Huygens' principle, Snell's law of refraction of a plane wave propagating from a denser to a rarer medium.(iii) When monochromatic light is incident on a surface separation two media, the reflected and refracted light both have the same frequency. Explain

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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State Huygens' principle. Using this principle draw a diagram to show how a plane wavefront incident at the interface of the two media gets refracted when it propagates from a rarer to a denser medium. Hence, verify Snqll's law of

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) A plane wavefront approaches a plane surface separating two media. If medium 1 is optically denser and medium 2 is optically rarer, using Huygens' principle, explain and show how a refracted wavefront is ^constructed?(ii) Verify Snell's law.(iii) When a light wave travels from a rarer to a denser medium, the speed decreases. Does it imply reduction in its energy?

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) Consider two coherent sources `S_1 and S_2` producing monochromatic waves to produce interference pattern. Let, the displacement of the wave produced by `S_1` be given by `Y_1 = acosomegat` and the displacement by `S_2` be `Y_2 = acos(omegat +phi)` Find out the expression for the amplitude of the resultant displacement at a point and show that the intensity at that point will be `I = 4a^2 cos^2phi/2` Hence, establish the conditions for constructive and destructive interference.(ii) What is the effect on the interference fringes in Young's double slit experiment when (i) the width of the source slit is increased;

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) In Young's double slit experiment, describe briefly how bright and dark fringes are obtained on the screen kept in front of a double slit. Hence, obtain the expression for the fringe width. (ii) The ratio of the intensities at minima to the maxima in the Young's double slit experiment is 9:25.Find the ratio of the widths of the two

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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(i) (a) 'Two independent monochromatic sources of light cannot produce `a` sustained interference pattern'. Give reason.(b) Light waves each of amplitude a and frequency `omega` emanating from two coherent light sources superpose at a point. If the displacements due to these waves is given by `Y_1 = acosomegat and Y_2 = acos(omegat+phi)` where `(phi)` is the phase difference between the two, obtain the expression for the resultant intensity at the point. (ii) In Young's double slit experiment using monochromatic light of wavelength `lambda`, the intensity of light at a point on the screen where path difference is `lambda`, is K

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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