Nuclei — Physics STD 12 Science — Question

Hydrogen (H), deuterium (D), singly ionized helium ( and doubly ionized lithium (Li) all have one electron around the nucleus. Consider n =2 to n = 1 transition. The wavelengths of emitted radiations are  and   respectively. Then approximately

(a)	(b) 4
(c)	(d)

. A surface that has the same electrostatic potential at every point on it is known as _____________.

Assertion   :  The magnetic filed at the ends of a very long current carrying solenoid is half of that at the center.

Reason      : If the solenoid is sufficiently long, the field within it is uniform.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

A radioactive substance has a half-life of 1 year. The fraction of this material, that would remain after 5 years will be

(a)

(b)

(c)

(d)

Equivalent energy of mass equal to 1 a.m.u. is

(a) 931 KeV

(b) 931 eV

(c) 931 MeV

(d) 9.31 MeV

The length of a given cylindrical wire is increased by 100 %.  Due to the consequent decrease in diameter the change in the resistance of the wire will be

(a) 300 %

(b) 200 %

(c) 100 %

(d) 50 %

Three long, straight parallel wires carrying current, are arranged as shown in figure. The force experienced by a 25 cm length of wire C is

(a) 10-3 N

(b) 2.5 ×10-3 N

(c) Zero

(d) 1.5 × 10-3 N

The graph which represents the correct variation of logarithm of activity (log A) versus time, in figure is

(a) A

(b) B

(c) C

(d) D

Which of the following group is diamagnetic?