Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

Identify the part of the electromagnetic spectrum used in
(i) radar and
(ii) eye surgery. Write their frequency range.

Name the radiation of the electromagnetic spectrum which is used for the following:

Radar and Give the frequency range.

Name the radiation of the electromagnetic spectrum which is used for the following:

To photograph internal parts of the human body and Give the frequency range

Name the radiation of the electromagnetic spectrum which is used for the following:

For taking photographs of the sky during the night and foggy conditions . Give the frequency range

The work function of aluminum is 4⋅2 eV. If two photons each of energy 2⋅5 eV are incident on its surface, will the emission of electrons take place? Justify your answer.

Define a wavefront. Using 'Huygens' principle, draw the shape of a refracted wavefront, when a plane wave is incident on a convex lens.

An electron moves along +x direction. It enters into a region of uniform magnetic field `vec B` directed along −z direction as shown in fig. Draw the shape of the trajectory followed by the electron after entering the field.

Gamma rays and radio waves travel with the same velocity in free space. Distinguish between them in terms of their origin and the main application.

A plane wave front AB propagating from denser medium (1) into a rarer medium (2) is incident on the surface P₁P₂ separating the two media as shown in fig.

Using Huygen’s principle, draw the secondary wavelets and obtain the refracted wave front in the diagram.

The magnitude of the electric field (in NC ^{– 1}) in a region varies with the distance r(in m) as

E = 10 r + 5

By how much does the electric potential increase in moving from point at r = 1 m to a point at r = 10 m.

Answer briefly.

Give two uses of radio waves.

A short bar magnet placed with its axis at 30° with a uniform external magnetic field of 0.25 T experiences a torque of magnitude equal to 4.5 × 10^–2 J. What is the magnitude of magnetic moment of the magnet?

A closely wound solenoid of 800 turns and area of cross-section 2.5 × 10^–4 m² carries a current of 3.0 A. Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment?

A closely wound solenoid of 2000 turns and area of cross-section 1.6 × 10^–4 m², carrying a current of 4.0 A, is suspended through its centre allowing it to turn in a horizontal plane.

1. What is the magnetic moment associated with the solenoid?
2. What is the force and torque on the solenoid if a uniform horizontal magnetic field of 7.5 × 10^–2 T is set up at an angle of 30° with the axis of the solenoid?

A closely wound solenoid of 2000 turns and area of cross-section 1.6 × 10^-4 m² , carrying a current of 4.0 A, is suspended through its centre allowing it to turn in a horizontal plane.

What is the force and torque on the solenoid if a uniform horizontal magnetic field of 7.5 × 10^-2 T is set up at an angle of 30° with the axis of the solenoid?

If the bar magnet is turned around by 180°, where will the new null points be located?

A 100 Ω resistor is connected to a 220 V, 50 Hz ac supply.

1. What is the rms value of current in the circuit?
2. What is the net power consumed over a full cycle?

A 100 Ω resistor is connected to a 220 V, 50 Hz ac supply.

What is the net power consumed over a full cycle?

Electric potential energy of two point charges q and q₀ is ________.

If a positive charge moves opposite to the direction of the electric field, the field does _______ work on charge and potential energy ________.