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

According to de-Broglie, the de-Broglie wavelength for electron in an orbit of hydrogen atom is 10^–9 m. The principle quantum number for this electron is

(a) 1

(b) 2

(c) 3

(d) 4

A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one- fourth of the material remains is

(a) 1080

(b) 2430

(c) 3240

(d) 4860

A horizontal rod of mass 10 gm and length 10 cm is placed on a smooth plane inclined at an angle of 60° with the horizontal, with the length of the rod parallel to the edge of the inclined plane. A uniform magnetic field of induction B is applied vertically downwards. If the current through the rod is 1.73 ampere, then the value of B for which the rod remains stationary on the inclined plane is

(a) 1.73 Tesla

(b)  Tesla

(c) 1 Tesla

(d) None of the above

A capacitor acts as an infinite resistance for:

In parallel combination of capacitors, the effective capacitance:

How much energy in kilowatt hour is consumed in operating ten 50 watt bulbs for 10 hours per day in a month (30 days).

(a) 1500

(b) 5,000

(c) 15

(d) 150

In optical instruments, the lenses are used to form images by:

There is a uniform electric field of strength   along y-axis. A body of mass 1g and charge is projected into the field from origin along the positive x-axis with a velocity 10m/s. Its speed in m/s after 10s is (Neglect gravitation)

(a) 10

(b) 5

(c) 10

(d) 20

A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 hours. The mean terminal voltage during discharge is 14 V. The "Watt-hour" efficiency of the battery is

(a) 82.5%

(b) 80 %

(c) 90%

(d) 87.5%