Atoms — Physics STD 12 Science — Question

A point object is placed at a distance of 30 cm from a convex mirror of focal length 30cm. The image will form at

(a) Infinity	(b) Focus
(c) Pole	(d) 15 cm behind the mirror

The magnetic flux linked with a loop of wire placed in a magnetic field does not depend upon :

According to Maxwell's equation, the velocity of light in any medium is expressed as.

The electric potential of free space is :

Two infinitely long parallel conducting plates having surface charge densities +σ and -σ respectively, are separated by a small distance. The medium between the plates is vacuum. If  is the dielectric permittivity of vacuum, then the electric field in the region between the plates is

(a) 0 volts/meter

(b)  volts/meter

(c)  volts/meter

(d)  volts/meter

Assertion :   Penetrating power of X-rays increases with the increasing the wavelength.

Reason    : The penetrating power of X-rays increases with the frequency of X-rays.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If assertion is false but reason is true.

In Young's double slit experiment how many maximas can be obtained on a screen (including the central maximum) on both sides of the central fringe if λ = 2000 and d = 7000  

(a) 12

(b) 7

(c) 18

(d) 4

Two sources give interference pattern which is observed on a screen, D distance apart from the sources. The fringe width is 2w. If the distance D is now doubled, the fringe width will

(a) Become w/2

(b) Remain the same

(c) Become w

(d) Become 4w

For a common base amplifier, the values of resistance gain and voltage gain are 3000 and 2800 respectively. The current gain will be:

An electron rotating in a circular path of radius r making n revolutions per second. Magnetic moment of electron will be: