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CLASS - XII PHYSICS (Unit –Optics) 1 What is the Brewster angle for air to glass transition? (𝜇𝑔=1.5) [1] 2 Draw a diagram to show cylindrical wavefront? [1] 3 A substance has critical angle of 45o for yellow light. What is its refractive index? [1] 4 In a telescope the focal length of the objective and the eye piece are 60cm and 5cm respectively. What is (1) its magnification power (2) tube length? [1] 5 Show the variation of u an v in case of a convex mirror? [1] 6 Write two points of difference between interference and diffraction? [2] 7 Obtain an expression for the ratio of intensities at maxima and minima in an interference pattern [2] 8 Can white light produce interference? What is the nature? [2] 9 How the focal lengths of a lens change with increase in the wavelength of the light? [2] 10 Thin prism of angle 60o gives a deviation of 30o. What is the refractive index of material of the prism? [2] State Brewster law? Using this law prove that at the polarizing angle of incidence, the reflected and transmitted rays are perpendicular to each other? [3] 11 12 In a single slit experiment, how is the angular width of central bright fringe maximum changed when 1) The slit width increased. 2) The distance between the slit and the screen is increased. 3) Light of smaller wavelength is used. 13 14 15 16 17 [3] What is polarization of light? What type of waves show the property of polarization? Name any two methods to produce plane polarized light? [3] Draw the curve depicting, variation of intensity in the interference pattern in young’s double slit experiment. State conditions for obtaining sustained interference of light? [3] Show that the limiting value of the angle of prism is twice its critical angle? Hence define critical angle. [3] Derive the expression for the angle of deviation for a ray of light passing through an equilateral prism of refracting angle A? [3] Derive the relation 1 𝑓 = 1 𝑓1 + 1 𝑓2 where 𝑓1 and 𝑓2 and f is the focal length of the combination in [3] contact. 18 A convex lens has a focal length 0.2m and made of glass is immersed in water (𝜇 = 1.33)Find the change in focal length of the lens? [3] 19 A reflecting type telescope has a concave reflector of radius of curvature 120 cm. Calculate the focal length of eye piece to secure a magnification of 20? [3] Define total internal reflection of light? Hence write two advantages of total reflecting prisms over a plane mirror? [3] 20 21 [3] 22 [3] 23 i) [4] 24 Prove that 𝑛2 𝑣 𝑛 = 𝑣1 = 𝑛2 −𝑛1 𝑅 When refraction occurs of a convex spherical refracting surface and the ray travels from rarer to denser medium. [5] 25 [5] 26 By stating sign conventions and assumptions used to derive the relation between u, v and f in case of a concave mirror? [5]