If a transformer of an audio amplifier has output impedance 8000 Ω and the speaker has input impedance of 8 Ω, the primary and secondary turns of this transformer connected between the output of amplifier and to loud speaker should have the ratio

• 1000 : 1

• 100 : 1

• 1 : 32

• 32 : 1

52.

In the electromagnetic spectrum, the visible spectrum lies between

• radiowaves and microwaves

• infrared and ultraviolet rays

• microwaves and infrared spectrum

• X-ray and γ-ray spectrum

Maxwell in his famous equation of electromagnetism introduced the concept

• AC current

• DC current

• displacement current

• impedance

Out of the following electromagnetic radiations, which has the shortest wavelength ?

• Radiowaves

• Infrared

• X-rays

• Visible light

A charged oil drop of mass 9.75 x 10^-15 kg and charge 30 x 10^-16 C is suspended in a uniform electric field existing between two parallel plates. The field between the plates, taking (g = 10 ms^-2) is

• 3.25 V/m

• 300 V/m

• 325 V/m

• 32.5 V/m

In Young's double slit experiment, the width of one of the slits is slowly increased to make it twice the width of the other slit. Then in thei nterference pattern 

• the intensity of maxima increase while that of minima decrease

• the intensities of both maxima and minima decrease

• the intensities of both maxima and minima increase

• the intensity of maxima decrease while that of minima increase

Two coherent sources whose intensity ratio is 81 : 1 produce interference fringes. The ratio of minimum to maximum intensity, i,e I_min : I_max is

• 16 : 25

• 9 : 1

• 1 : 9

• 25 : 16

An infinitely long rod lies along the axis of concave mirror of focal length f. The near end of the rod is at a distance x > f from the mirror. Then the length of the image of the rod is

• $\frac{{\mathrm{f}}^2}{\mathrm{x} + \mathrm{f}}$

• $\frac{{\mathrm{f}}^2}{\mathrm{x}}$

• $\frac{{\mathrm{f}}^2}{\mathrm{x} - \mathrm{f}}$

• $\frac{\mathrm{xf}}{\mathrm{x} + \mathrm{f}}$

A beaker containing a liquid appears to be half when it is actually two third full. The refractive index of liquid is

• 7/6

• 6/5

• 4/3

• 5/4

If h₁ and h₂ are the heights of the images in conjugate position of a convex lens, then the height of the object is

• h₁ + h₂

• h₁ − h₂

• h₁/h₂

• $\sqrt{{\mathrm{h}}_1{\mathrm{h}}_2}$