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

A freshly prepared radioactive source of half-life 2h emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source is:

Which scientist proposed the concept of atomic mass?

An electric dipole is placed at the centre of a sphere.
Mark the correct options:

Ultraviolet radiations of 6.2eV  falls on an aluminium surface (work function 4.2 eV). The kinetic energy in joules of the fastest electron emitted is approximately

(a) 3.2

(b) 3.2

(c) 3.2

(d) 3.2

The voltage gain of the following amplifier is

(a) 10

(b) 100

(c) 1000

(d) 9.9

The angular momentum of the electron in hydrogen atom in the ground state is:

A nuclear reaction given by   represents

(a) g-decay

(b) Fusion

(c) Fission

(d) b-decay

In Young's double slit experiment, if monochromatic light is replaced by white light

(a) All bright fringes become white

(b) All bright fringes have colours between violet and red

(c) Only the central fringe is white, all other fringes are coloured

(d) No fringes are observed

A 50 volt potential difference is suddenly applied to a coil with   henry and R = 180 ohm. The rate of increase of current after 0.001 second is

(a) 27.3 amp/sec

(b) 27.8 amp/sec

(c) 2.73 amp/sec

(d) None of the above

A positively charged thin metal ring of radius R  is fixed in the xy - plane with its centre at the O. A negatively charged particle P  is released from rest at the point  (0, 0,  where  . Then the motion of  P is

(a) Periodic for all values of   satisfying 0 <

(b) Simple harmonic for all values of satisfying 0 <

(c) Approximately simple harmonic provided

(d) a, c