HOLIDAY HOME WORK PHYSICS CLASS-12B AUTUMN BREAK 2018

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1 HOLIDAY HOME WK PHYSICS CLASS-12B AUTUMN BREAK 2018 NOTE: 1. THESE QUESTIONS ARE FROM PREVIOUS YEAR BOARD PAPERS FROM CHAPTERS EMI,AC,OPTICS(BUT TRY TO SOLVE ONLY NON-REPEATED QUESTION) QUESTION PAPER CODE 51/1/1 CBSE DELHI In a single slit diffraction experiment, when a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why? 2. State two points of difference between the interference patterns obtained in Young s double slit experiment and the diffraction pattern due to a single slit. 3. (a) Define self-inductance. Write its S.I. units.(b) Derive an expression for selfinductance of a long, solenoid of length l, cross sectional area A having N number of turns. 4. Three light rays red (R), green (G) and blue (B) are incident on a right angled prism abc at face ab. The refractive indices of the material of the prism for red, green and blue wavelengths are 1.39, 1.44 and 1.47 respectively. Out of the three which colour ray will emerge out of face ac? Justify your answer. Trace the path of these rays after passing through face ab. 5. (a) Derive an expression for the average power consumed in a series LCR circuit connected to a.c. source in which the phase difference between the voltage and the current in the circuit is φ. (b) Define the quality factor in an a.c. circuit. Why should the quality factor have high value in receiving circuits? Name the factors on which it depends. 6. or (a)derive the relationship between the peak and the rms value of current in an a.c. circuit. (b) Describe briefly, with the help of a labelled diagram, working of a step-up transformer. A step-up transformer converts a low voltage into high voltage. Does it not violate the principle of conservation of energy? Explain. 7. 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 nl and n2. Establish the relation between the distances of the object, the image and the radius of curvature from the central point of the spherical surface. Hence derive the expression of the lens maker s formula. Draw the labelled ray diagram for the formation of image by a compound microscope. Derive the expression for the total magnification of a compound microscope. Explain why both the objective and the eyepiece of a compound microscope must have short focal lengths. QUESTION PAPER CODE 51/1/1 CBSE 2010 DELHI 1. A plot of magnetic flux (φ) versus current (I) is shown in the figure for two inductors A and B. Which of the two has larger value of self-inductance? 2. A glass lens of refractive index 1.45 disappears when immersed in a liquid. What is the value of refractive index of the liquid? 3. State the conditions for the phenomenon of total internal reflection to occur.

2 4. An electric lamp having coil of negligible inductance connected in series with a capacitor and an AC source is glowing with certain brightness. How does the brightness of the lamp change on reducing the (i) capacitance, and (ii) the frequency? Justify your answer. 5. The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm.if focal length of the lens is 12 cm, find the refractive index of the material of the lens. 6. (a) The bluish colour predominates in clear sky. (b) Violet colour is seen at the bottom of the spectrum when white light is dispersed by a prism. State reasons to explain these observations. 7. What is an unpolarized light? Explain with the help of suitable ray diagram how an unpolarized light can be polarized by reflection from a transparent medium. Write the expression for Brewster angle in terms of the refractive index of denser medium. 8. Describe briefly, with the help of a labelled diagram, the basic elements of an A.C. generator. State its underlying principle. Show diagrammatically how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf induced in the rotating loop. A series LCR circuit is connected to an ac source having voltage ν = νm sin ωt.derive the expression for the instantaneous current I and its phase relationship to the applied voltage. Obtain the condition for resonance to occur. Define power factor. State the conditions under which it is (i) maximum and (ii) minimum. 9. State Huygens s principle. Show, with the help of a, suitable diagram, how this principle is used to obtain the diffraction pattern by a single slit. Draw a plot of intensity distribution and explain clearly why the secondary maxima become weaker with increasing order (n) of the secondary maxima. 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 eye piece has a focal length of 5 cm and the final image is formed at the near point, estimate the magnifying power of the microscope. QUESTION PAPER CODE 51/1/ CBSE DELHI 1. Define the term 'wattless current' When monochromatic light travels from one medium to another its wavelength changes but frequency remains the same, Explain Two convex lenses of same focal length but of aperture A1 and A2 (A2 < A1), are used as the objective lenses in two astronomical telescopes having identical eyepieces. What is the ratio of their resolving power? Which telescope will you prefer and why? Give reason. 4. (i) Define modulation index. (ii) Why is the amplitude of modulating signal kept less than the amplitude of carrier wave? 5. A current is induced in coil C1 due to the motion of current carrying coil C2.(a)Write any two ways by which a large deflection can be obtained in the galvanometer G. (b)

3 Suggest an alternative device to demonstrate the induced current in place of a galvanometer. 6. Describe Young's double slit experiment to produce interference pattern due to a monochromatic source of light. Deduce the expression for the fringe width. Use Huygens s principle to verify the laws of refraction. 7. (a) Describe briefly, with the help of suitable diagram, how the transverse nature of light can be demonstrated by the phenomenon of polarization. (b) When unpolarized light passes from air to a transparent medium, under what condition does the reflected light get polarized? 8. (a) 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. (b) Explain briefly how the phenomenon of total internal reflection is used in fibre optics. (a)obtain lens makers formula using the expression Here the ray of light propagating from a rarer medium of refractive index (n1) to a denser medium of refractive index (n2) is incident on the convex side of spherical refracting surface of radius of curvature R. (b) Draw a ray diagram to show the 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 formed. 9. (i) With the help of a labelled diagram, describe briefly the underlying principle and working of a step up transformer.(ii) Write any two sources of energy loss in a transformer.(iii) A step up transformer converts a low input voltage into a high output voltage. Does it violate law of conservation of energy? Explain. Derive an expression for the impedance of a series LCR circuit connected to an AC supply of variable frequency. Plot a graph showing variation of current with the frequency of the applied voltage. Explain briefly how the phenomenon of resonance in the circuit can be used in the tuning mechanism of a radio or a TV set. QUESTION PAPER CODE 51/1/ Under what condition does a biconvex lens of glass having a certain refractive index act as a plane glass sheet when immersed in a liquid? 2. A ray of light, incident on an equilateral glass prism (μg = 3) moves parallel to the base line of the prism inside it. Find the angle of incidence for this ray. 3. Define self-inductance of a coil. Show that magnetic energy required to build up the current I in a coil of self-inductance L is given by 4. A metallic rod of 'L' length is rotated with angular frequency of 'ω' with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius L, about an axis passing through the centre and perpendicular to the plane of the ring. Constant and uniform magnetic field B parallel to the axis is presents everywhere. Deduce the expression for the emf between the centre and the metallic ring. 5. The figure shows a series LCR circuit with L = 5.0 H, C = 80 μf, R = 40 Ω connected to a variable frequency 240 V source. Calculate 3 (i) The angular frequency of the source which drives the circuit at resonance. (ii) The current at the resonating frequency.

4 (iii) The rms potential drop across the capacitor at resonance. 6. (A)Why are coherent sources necessary to produce a sustained interference pattern?(b) In Young's double slit experiment using monochromatic light of wavelength λ,the intensity of light at a point on the screen where path difference is λ, is K units. Find out the intensity of light at a point where path difference is λ/3. 7. Use Huygens's principle to explain the formation of diffraction pattern due to a single slit illuminated by a monochromatic source of light. When the width of the slit is made double the original width, how would this affect the size and intensity of the central diffraction band? 8. Define magnifying power of a telescope. Write its expression. A small telescope has an objective lens of focal length 150 cm and an eye piece 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 eye piece. 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 adjustment. CBSE AISSCE 2013 SET 1 1. Which of the following waves can be polarized (i) Heat waves (ii) Sound waves? Give reason to support your answer. 2. (a) Write the necessary conditions for the phenomenon of total internal reflection to occur. (b) Write the relation between the refractive index and critical angle for a given pair of optical media. 3. State Lenz s Law, A metallic rod held horizontally along east west direction, is allowed to fall under gravity. Will there be an emf induced at its ends? Justify your answer. 4. A convex lens of focal length 25 cm is placed coaxially in contact with a concave lens of focal length 20 cm. Determine the power of the combination. Will the system be converging or diverging in nature? 5. A metallic rod of length l is rotated with a frequency v with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius r, about an axis passing through the centre and perpendicular to the plane of the ring. A constant uniform magnetic field B parallel to the axis is present everywhere. Using Lorentz force, explain how emf is induced between the centre and the metallic ring and hence obtain the expression for it. 6. (a) In what way is diffraction from each slit related to the interference pattern in a double slit experiment? (b) Two wavelengths of sodium light 590nm and 596 nm are used, in turn, to study the diffraction taking place at a single slit of aperture 2x10-4 m. The distance between the slit and the screen is 1.5 m. Calculate the separation between the positions of the first maxima of the diffraction pattern obtained in the two cases. 7. In a series LCR circuit connected to an ac source of variable frequency and voltage V = V0 Sinωt, draw a plot showing the variation of current (i) with angular frequency ωfor two different values of resistance R1 and R2( R1 > R2). Write the condition under which the phenomenon of resonance occurs. For which value of the resistance out of the two curves, a sharper resonance is produced? Define Q factor of the circuit and give its significance. 8. (a) Draw a ray diagram showing the image formation by a compound microscope. Hence obtain expression for total magnification when the image is formed at infinity. (b)

5 Distinguish between myopia and hypermetropia. Show diagrammatically how these defects can be corrected. or (a) State Huygens s 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 Snell s law of refraction. (i) When monochromatic light travels from a rarer to a denser medium, explain the following, giving reasons: (i) Is the frequency of reflected and refracted light same as the frequency of incident light? (ii) Does the decrease in speed imply a reduction in the energy carried by light wave? CBSE 2014 DELHI PHYSCIS PAPER SET-1 1. Two independent monochromatic sources of light cannot produce a sustained interference pattern. Give reason. (ii) Light waves each of amplitude a and frequency ω, emanating from two coherent light sources superpose at a point. If the displacements due to these waves is given by Y1= a cosωt and y2= cos(wt + Φ) where Φ is the phase difference between the two, obtain the expression for the resultant intensity at the point.(b) In Young s double slit experiment, using monochromatic light of wavelength A, the intensity of light at a point on the screen where path difference is, is k units. Find out the intensity of light at a point where path difference is λ/3. 2. (a) How does one demonstrate, using a suitable diagram, that unpolarised light when passed through a polaroid gets polarised? (1 ) A beam of unpolarised light is incident on a glass-air interface. Show, using a suitable ray diagram, that light reflected from the interface is totally polarised, when µ = tanib where µ is the refractive index of glass with respect to air and is the Brewster s angle.

Section A Conceptual and application type questions. 1 Which is more observable diffraction of light or sound? Justify. (1)

$Section A Conceptual and application type questions. 1 Which is more observable diffraction of light or sound? Justify. (1)$ INDIAN SCHOOL MUSCAT Department of Physics Class : XII Physics Worksheet - 6 (2017-2018) Chapter 9 and 10 : Ray Optics and wave Optics Section A Conceptual and application type questions 1 Which is more