Nuclei — Physics STD 12 Science — Question

A combination of two thin lenses of the same material with focal lengths  and , arranged on a common axis minimizes chromatic aberration, if the distance between them is

(a)

(b)

(c) (

(d)

Figure shows the displacement-time graph of a particle moving on the X-axis.

1. The particle is continuously going in positive x direction.
2. The particle is at rest.
3. The velocity increases up to a time to, and then becomes constant.
4. The particle moves at a constant velocity up to a time to, and then stops.

Inductive reactance of a coil is expressed in.

In a metre bridge experiment null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y. If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4X against Y

(a) 50 cm

(b) 80 cm

(c) 40 cm

(d) 70 cm

The resistance of 10 metre long potentiometer wire is 1ohm/meter. A cell of e.m.f. 2.2 volts and a high resistance box are connected in series to this wire. The value of resistance taken from resistance box for getting potential gradient of 2.2 millivolt/metre will be

(a) 790 Ω

(b) 810 Ω

(c) 990 Ω

(d) 1000 Ω

The network shown in the figure is a part of a complete circuit. If at a certain instant the current i is 5 A and is decreasing at the rate of   then   is

(a) 5 V

(b) 10 V

(c) 15 V

(d) 20 V

Which of the following is not equal to watt

(a)

(b) Amp / Volt

(c) Amp × Volt

(d) Joule / sec

A ball of mass 1 g and charge   moves from a point A. where potential is 600 volt to the point B where potential is zero. Velocity of the ball at the point B is 20 cm/s. The velocity of the ball at the point A will be

(a) 22.8 cm/s

(b) 228 cm/s

(c) 16.8 m/s

(d) 168 m/s

The minimum orbital angular momentum of the electron in a hydrogen atom is:

Assertion :   Photosensitivity of a metal is high if its work function is small.

Reason     : Work function =   where   is the threshold frequency.

(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 the assertion and reason both are false.