Class 12th

The correct relation between α (ratio of collector current to emitter current) and β (ratio of collector current to base current) of a transistor is :

Let the tangent to the circle x² + y² = 25 at the point R(3,4) meet x-axis and y-axis at points P and Q, respectively. If r is the radius of the circle passing through the origin O and having centre at the incentre of the triangle OPQ, then r² is equal to:

The number of solution of the equation x + 2tanx = π/2 in the interval [0, 2π] is:

The decay of a proton to neutron is :

Three rays of light, red (R), green (G) and blue (B) are incident on the face PQ of a right angled prism PQR as shown in the figure. The refractive indices of material of the prism for red, green and blue wavelength are 1.27, 1.42 and 1.49 respectively. The colour of ray(s) emerging out of the face PR is

If x, y, z are in arithmetic progression with common difference d, x≠3d, and the determinant of the matrix [[3, 4√2, x], [4, 5√2, y], [5, k, z]] is zero, then the value of k² is:

Two tangents are drawn from a point P to the circle x² + y² - 2x - 4y + 4 = 0, such that the angle between these tangents is tan⁻¹(12/5), where tan⁻¹(12/5) ∈ (0,π). If the centre of the circle is denoted by C and these tangents touch the circle at points A and B, then the ratio of the areas of ΔPAB and ΔCAB is:

The time taken for the magnetic energy to reach 25% of its maximum value, when solenoid of resistance R, inductance L is connected to a battery, is:

A proton and an α-particle, having kinetic energy Kp and Kα respectively, enter into a magnetic field at right angles. The ratio of the radii of trajectory of proton to that of α-particle is 2 : 1. The ratio of Kp : Kα is

If the equation of plane passing through the mirror image of a point (2,3,1) with respect to line (x+1)/2 = (y-3)/1 = (z+2)/-1 and containing the line (x-2)/3 = (1-y)/2 = (z+1)/1 is, αx + βy + γz = 24 then α + β + γ is equal to: