Wave Optics — Physics STD 12 Science — Question

A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a

(a) Convergent lens of focal length 3.5 R

(b) Convergent lens of focal length 3.0 R

(c) Divergent lens of focal length 3.5 R

(d) Divergent lens of focal length 3.0 R

The distance moved by a particle in simple harmonic motion in one time period is:

1. A
2. 2A
3. 4A
4. zero.

The energy in MeV is released due to transformation of 1 kg mass completely into energy (c = 3 

(a) 7.625 ×10 MeV

(b) 10.5

(c) 2.8

(d) 5.625

An electric dipole is situated in an electric field of uniform intensity E whose dipole moment is p and moment of inertia is I. If the dipole is displaced slightly from the equilibrium position, then the angular frequency of its oscillations is

(a)

(b)

(c)

(d)

Three infinitely long charge sheets are placed as shown in figure. The electric field at point P is

(a)

(b)

(c)

(d)

Five resistances are connected as shown in the figure. The effective resistance between the points A and B is

(a)

(b)

(c) 15 Ω

(d) 6 Ω

The thermo e.m.f. of a thermo-couple is 25μV/℃  at room temperature. A galvanometer of 40 ohm resistance, capable of detecting current as low as ,  is connected with the thermocouple. The smallest temperature difference that can be detected by this system is

(a) 20 ℃

(b) 16 ℃

(c) 12 ℃

(d) 8℃

A horizontal circular loop carries a current that looks clockwise when viewed from above. It is replaced by an equivalent magnetic dipole consisting of a south pole S and a north pole N:

1. The line SN should be along a diameter of the loop.
2. The line SN should be perpendicular to the plane of the loop.
3. The south pole should be slow the loop.
4. The north pole should be below the loop.

Two wave pulses travel in opposite directions on a string and approach each other. The shape of one pulse is inverted with respect to the other.

1. The pulses will collide with each other and vanish after collision.
2. The pulses will reflect from each other i.e., the pulse going towards right will finally move towards left and vice versa.
3. The pulses will pass through each other but their shapes will be modified.
4. The pulses will pass through each other without any change in their shapes.

A battery of e.m.f. E and internal resistance r is connected to a variable resistor R as shown here. Which one of the following is true

(a) Potential difference across the terminals of the battery is maximum when R = r

(b) Power delivered to the resistor is maximum when R = r

(c) Current in the circuit is maximum when R = r

(d) Current in the circuit is maximum when R >> r