Electromagnetic Waves — Physics STD 12 Science — Question

The atomic number and mass number for a specimen are Z and A respectively. The number of neutrons in the atom will be :

An object approaches a convergent lens from the left of the lens with a uniform speed 5 m/s and stops at the focus. The image

The refractive index of water with respect to air is 4 / 3 and the refractive index of glass with respect to air is 3/2. The refractive index of water with respect to glass is

(a)

(b)

(c)

(d) 2

A radioactive sample has  active atoms at t = 0. If the rate of disintegration at any time is R and the number of atoms is N, then the ratio R/N varies with time as

(a)

(b)

(c)

(d)

The toroid of radius 10 cm has 100 turns. If a current of 0.1 ampere is flowing in it, then the value of the magnetic field on the axis of the toroid will be:

What is the induced dipole moment developed per unit volume of a dielectric when placed in an external electric field called?

Assertion :  Electric field outside the conducting wire which carries a constant current is zero.

Reason    : Net charge on conducting wire is zero.

(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.

The composition of an a -particle  can be expressed as

(a) 1 P + 1 N

(b) 1 P + 2 N

(c) 2 P + 1 N

(d) 2 P + 2 N

Mark the correct options:

A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence, the rod gains gravitational potential energy. The work required to do this comes from: