IIT-JEE-Physics-2006

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1.     Given

        R₁ = 1Ω             C₁ = 2μF

        R₂ = 1Ω             C₂ = 4μF

        The times constants (in mS) for the circuits I, II, III are respectively

        (A)    18, 8/9, 4

        (B)    18, 4, 8/9

        (C)    4, 8/9, 18

        (D)    8/9, 18, 4

2.     Two blocks A and B of masses 2m and m, respectively, are connected by a massles and inextensible string. The whole system is suspended by a massless spring as shown in the figure. The magnitudes of acceleration of A and B, immediately after the string is cut, are respectively

        (A)    g, g/2

        (B)    g/2, g

        (C)    g, g

        (D)    g/2, g/2

3.     A point object is placed at a distance of 20 cm from a thin plani-convex lens of focal length 15 cm, fi the plane surface is silvered. The image will form at

        (A)    60 cm left of AB

        (B)    30 cm left of AB

        (C)    12 cm left of AB

        (D)    60 cm right of AB

4.     A biconvex lens of focal length f forms a circular image of sun of radius r in focal plane. Then

        (A)    Πr² œ f

        (B)    Πr² œ f²

        (C)    if lower half part is covered by black sheet, then area of the image is equal to Πr²/2

        (D)    if f is doubles, intensity will increase

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