Nuclei — Physics STD 12 Science — Question

The magnetic field of earth is due to

(a) Motion and distribution of some material in and outside the earth

(b) Interaction of cosmic rays with the current of earth

(c) A magnetic dipole buried at the centre of the earth

(d) Induction effect of the sun

The two alpha particles are released along with energy, when Li-7 is bombarded with a proton. It was found that the mass of the two alpha particles weighs less that the original product in the reaction. Now the mass that was converted to energy is called as:

Calculate the de-Brogile wavelength of an electron travelling at 1% of the speed of light:

In Young's double slit experiment, if the slit widths are in the ratio 1 : 9, then the ratio of the intensity at minima to that at maxima will be

(a) 1

(b) 1/9

(c) 1/4

(d) 1/3

A large nonconducting sheet M is given a uniform charge density. Two uncharged small metal rods A and B are placed near the sheet as shown in figure:

1. M attracts A.
2. M attracts B.
3. A attracts B.
4. B attracts A.

When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor:

1. Increases.
2. Decreases.
3. Remains the same.
4. Becomes zero.

A beaker containing a liquid is kept inside a big closed jar. If the air inside the jar is continuously pumped out the pressure in the liquid near the bottom of the liquid will:

1. Increase
2. Decrease
3. Remain constant
4. First decrease and then increase.

An electromagnetic wave is propagating along Y-axis. Then.

Energy levels A, B, C of a certain atom corresponding to increasing values of energy i.e. . If  are the wavelengths of radiations corresponding to the transitions C to B, B to A and C to A respectively, which of the following statements is correct

(a)

(b)

(c)

(d)