Magnetism And Matter — Physics STD 12 Science — Question

Which of the following curves may represent the speed of the electron in a hydrogen atom as a function of the principal quantum number n?

A bar magnet when placed at an angle of 30^o to the direction of magnetic field induction of 5 × 10^–2 T, experiences a moment of couple 25 × 10^–6 N-m. If the length of the magnet is 5 cm its pole strength is

(a) 2 × 10–2 A-m

(b) 5 × 10–2 A-m

(c) 2 A-m

(d) 5 A-m

Through which character we can distinguish the light waves from sound waves

(a) Interference

(b) Refraction

(c) Polarisation

(d) Reflection

The potentials of the two plates of capacitor are +10V and –10 V. The charge on one of the plates is 40 C. The capacitance of the capacitor is

(a) 2 F

(b) 4 F

(c) 0.5 F

(d) 0.25 F

With the decrease in the wave length of the incident radiation the velocity of the photoelectrons emitted from a given metal

Let I_A and I_B be moments of inertia of a body about two axes A and B respectively. The axis A passes through the centre of mass of the body but B does not:

1. I_A < I_B.
2. If I_A < I_B, the axes are parallel.
3. If the axes are parallel, I_A < I_B.
4. If the axes are not parallel I_A > I_B.

Light of wavelength 589.3 nm  is incident normally on the slit of width 0.1 mm. What will be the angular width of the central diffraction maximum at a distance of 1 m  from the slit

(a) 0.68°

(b) 1.02°

(c) 0.34°

(d) None of these

A person wears glasses of power – 2.5 D. The defect of the eye and the far point of the person without the glasses are respectively

(a) Farsightedness, 40 cm	(b) Nearsightedness, 40 cm
(c) Astigmatism, 40 cm	(d) Nearsightedness, 250 cm

The figure shows a network of currents. The magnitude of currents is shown here. The current i will be

(a) 3 A

(b) 13 A

(c) 23 A

(d) – 3 A