Radiation and Dual Nature of Matter — Physics STD 12 Science — Question

The focal length of a convex lens is 10 cm and its refractive index is 1.5.  If the radius of curvature of one surface is 7.5 cm, the radius of curvature of the second surface will be

(a) 7.5 cm

(b) 15.0 cm

(c) 75 cm

(d) 5.0 cm

At a certain place the angle of dip is 30° and the horizontal component of earth's magnetic field is 0.50 Oersted. The earth's total magnetic field is

(a)

(b) 1

(c)

(d)

While tuning in a certain broadcast station with a receiver, we are actually

(a) Varying the local oscillator frequency

(b) Varying the frequency of the radio signal to be picked up

(c) Tuning the antenna

(d) None of these

A flat circular disc has a charge +Q uniformly distributed on the disc. A charge +q is thrown with kinetic energy  E towards the disc along its normal axis. The charge q  will

(a) Hit the disc at the centre

(b) Return back along its path after touching the disc

(c) Return back along its path without touching the disc

(d) Any of the above three situations is possible depending on the magnitude of E

Three capacitors each of capacity 4μF  are to be connected in such a way that the effective capacitance is 6 μF. This can be done by

(a) Connecting them in parallel	(b) Connecting two in series and one in parallel
(c) Connecting two in parallel and one in series	(d) Connecting all of them in series

Three equal capacitors, each with capacitance C are connected as shown in figure. Then the equivalent capacitance between  A and  B is

(a) C

(b) 3C

(c)

(d)

The radius of curvature of the curved surface of a plano-convex lens is 20 cm. If the refractive index of the material of the lens be 1.5, it will

A hot electric iron has a resistance of 80 Ω and is used on a 200 V source. The electrical energy spent, if it is used for two hours, will be

(a) 8000 Wh

(b) 2000 Wh

(c) 1000 Wh

(d) 800 Wh

In the figure is shown Young’s double slit experiment. Q is the position of the first bright fringe on the right side of O. P is the 11^th fringe on the other side, as measured from Q. If the wavelength of the light used is 6000 ,  then   will be equal to

(a) 6

(b) 6.6

(c) 3.138

(d) 3.144

If R is the Rydberg’s constant for hydrogen the wave number of the first line in the Lyman series will be

(a)

(b)

(c)

(d) 2R