Class 12th

A charge particle is moving in uniform magnetic field $\left(2\widehat{i}+3\widehat{j}\right)$ T. If it has an acceleration of $\left(\alpha \widehat{i}-4\widehat{j}\right)m/s^2$ , then the value of will be:

Given below are two statements:

Statement I : A second's pendulum has a time period of 1 second.

Statement II : It takes precisely one second to move between the two extreme positions.

In the light of the above statements, choose the correct answer from the options given below

In a series LR circuit X_L = R and power factor of the circuit is P₁. When capacitor with capacitance C such that X_L = X_C is put in series, the power factor becomes P₂. The ratio $\frac{P_1}{P_2}$  is:

The magnetic field of a plane electromagnetic wave is given by:

$\overrightarrow{B}=2*10^{-8}$ sin(0.5 * 10³x + 1.5 * 10¹¹t) $\widehat{j}$ T.

The amplitude of the electric field would be:

Given below are two statements : one is labeled as Assertion A and the other is labeled as Reason R.

Assertion A : For a simple microscope, the angular size of the object equals the angular size of the image.

Reason R : Magnification is achieved as the small object can be kept much closer to the eye that 25cm and hence it subtends a large angle.

In the light of the above statements, choose the most appropriate answer from the options given below:

A body mass 8kg and another of mass 2kg are moving with equal kinetic energy. Thee ratio of their respective momenta will be:

In Young's double slit experiment, the fringe width is 12mm. If the entire arrangement is placed in water refractive index $\frac{4}{3}$ , then the fringe width becomes (in mm):

Given below are two statements : one is labeled as Assertion A and the other is labeled as Reason R.

Assertion A : For a simple microscope, the angular size of the object equals the angular size of the image.

Reason R : Magnification is achieved as the small object can be kept much closer to the eye that 25cm and hence it subtends a large angle.

In the light of the above statements, choose the most appropriate answer from the options given below

A parallel beam of light of wavelength 900nm and intensity 100Wm^-2 is incident on a surface perpendicular to the beam. The number of photons crossing 1cm² area perpendicular to the beam in one second is:

An aeroplane, with its wings spread 10m, is flying at a speed of 180 km/h in a horizontal direction. The total intensity of earth's field at that part is 2.5 * 10^-4Wb/m² and the angle of dip is 60°. The emf induced between the tips of the plane wings will be