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

In producing a pure spectrum, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit:

1. Produces less diffraction.
2. Increases intensity.
3. Allows only one colour at a time.
4. Allows a more parallel beam when it passes through the lens.

Electromagnets are made of soft iron because soft iron has:

1. High retentivity and high coercive force.
2. High retentivity and low coercive force.
3. Low retentivity and high coercive force.
4. Low retentivity and low coercive force.

A current carrying solenoid is approaching a conducting loop as shown in the figure. The direction of induced current as observed by an observer on the other side of the loop will be

(a) Anticlockwise

(b) Clockwise

(c) East

(d) West

To deposit one litre of hydrogen at 22.4 atmosphere from acidulaled water, the quantity of electricity that must pass through is

(a) 1 coulomb

(b) 22.4 coulomb

(c) 96500 coulomb

(d) 193000 coulomb

A resistor of resistance R is connected to an ideal battery. If the value of R is decreased, the power dissipated in the resistor will:

In the case of bar magnet, lines of magnetic induction

(a) Start from the north pole and end at the south pole

(b) Run continuously through the bar and outside

(c) Emerge in circular paths from the middle of the bar

(d) Are produced only at the north pole like rays of light from a bulb

A achromatic combination is made with a lens of focal length f and dispersive power ω with a lens having dispersive power of 2ω. The focal length of second will be

(a) 2f

(b) f/2

(c) -f/2

(d) – 2 f

Which of the following sometimes requires initiation from a neutron?

For watt-less power in an AC circuit the phase angle between the current and voltage is.

In a wire of circular cross-section with radius r, free electrons travel with a drift velocity V when a current I flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is 2V

(a) 2I

(b) I

(c) I/2

(d) I/4