Radiation and Dual Nature of Matter — Physics STD 12 Science — Question

The electrical conductivity of pure germanium can be increased by:

1. Increasing the temperature.
2. Doping acceptor impurities.
3. Doping donor impurities.
4. Irradiating ultraviolet light on it.

Two ions have equal masses but one is singly-ionised and the other is doubly-ionised. They are projected from the same place in a uniform magnetic field with the same velocity perpendicular to the field.

To get three images of a single object, one should have two plane mirrors at an angle of

(a) 30°

(b) 60°

(c) 90°

(d) 150°

Two uniform solid spheres having unequal masses and unequal radii are released from rest from the same height on a rough incline. If the spheres roll without slipping:

1. The heavier sphere reaches the bottom first.
2. The bigger sphere reaches the bottom first.
3. The two spheres reach the bottom together.
4. The information given is not sufficient to tell which sphere will reach the bottom first.

Black hole is a

(a) Hole in the ozone layer of atmosphere

(b) Hole in earth's centre

(c) Highly dense matter available in the atmosphere

(d) Hole in troposphere

In the given figure the capacitors  have a capacitance 4mF each if the capacitor  has a capacitance 10mF, then effective capacitance between A and B will be

(a) 2mF

(b) 4mF

(c) 6mF

(d) 8mF

The audio signal:

A part of a long wire carrying a current i is bent into a circle of radius r as shown in figure. The net magnetic field at the centre O of the circular loop is

(a)

(b)

(c)

(d)

Figure given below shows a beam of light converging at point P.  When a convex lens of focal length 16 cm is introduced in the path of the beam at a place O shown by dotted line such that OP becomes the axis of the lens, the beam converges at a distance x from the lens.  The value x will be equal to

(a) 12 cm

(b) 24 cm

(c) 36 cm

(d) 48 cm

Which of the following quantities is zero on an average for the molecules of an ideal gas in equilibrium?

1. Kinetic energy.
2. Momentum.
3. Density.
4. Speed.