Class 12th

In the line spectra of hydrogen atom, difference between the largest and the shortest wavelengths of the Lyman series is 304Å. The corresponding difference for the Paschan series in Å is:

In a compound microscope, the magnified virtual image is formed at a distance of 25 cm from the eye-piece. The focal length of its objective lens is 1 cm. If the magnification is 100 and the tube length of the microscope is 20 cm, then the focal length of the eyepiece lens (in cm ) is

A battery of 3.0 V is connected to a resistor dissipating 0.5 W of power. If the terminal voltage of the battery is 2.5 V, the power dissipated within the internal resistance is:

Two charged thin infinite plane sheets of uniform surface charge density σ+and σ−, where |σ+| > |σ−|, intersect at right angle. Which of the following best represents the electric field lines for this system.

A two point charges 4q and –q are fixed on the x-axis at x = −d/2 and x = d/2, respectively. If a third point charge ' q ' is taken from the origin to x = d along the semicircle as shown in the figure, the energy of the charge will:

A small bar magnet placed with its axis at 30° with an external field of 0.06 T experiences a torque of 0.018Nm. The minimum work required to rotate it from its stable to unstable equilibrium position is:

The decreasing order of reactivity of the following organic molecules towards AgNO3 solution is:
(A) Cl
(B) Cl OMe
(C) CH3CHCH3 Cl
(D) CH3CHCH2NO2 Cl

A beam of plane polarized light of large cross-sectional area and uniform intensity of 3.3Wm⁻² falls normally on a polarizer (cross sectional area 3 * 10⁻⁴ m² ) which rotates about its axis with an angular speed of 31.4rad/s. The energy of light passing through the polariser per revolution, is close to:

Among statements (a) - (d), the correct ones are:

(a) Lime stone is decomposed to  during the extraction of iron from its oxides.

(b) In the extraction of silver, silver is extracted as an anionic complex.

(c) Nickel is purified by Mond's process.

(d) Zr and Ti are purified by Van Arkel method.

A wire A, bent in the shape of an arc of a circle, carrying a current of 2 A and having radius 2 cm and another wire B, also bent in the shape of arc of a circle, carrying a current of 3 A and having radius of 4 cm, are placed as shown in the figure. The ratio of the magnetic fields due to the wires A and B at the common centre O is: