Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Physics

There are two current carrying planar coils made each from identical wires of length L. C₁ is circular (radius R) and C₂ is square (side a). They are so constructed that they have same frequency of oscillation when they are placed in the same uniform B and carry the same current. Find a in terms of R.

Study the circuits (a) and (b) shown in figure and answer the following questions.

(a)

(b)

1. Under which conditions would the rms currents in the two circuits be the same?
2. Can the rms current in circuit (b) be larger than that in (a)?

Can the instantaneous power output of an ac source ever be negative? Can the average power output be negative?

The alternating current in a circuit is described by the graph shown in figure. Show rms current in this graph.

How does the sign of the phase angle `phi`, by which the supply voltage leads the current in an LCR series circuit, change as the supply frequency is gradually increased from very low to very high values.

One requires 11eV of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum frequency of the appropriate electromagnetic radiation to achieve the dissociation lies in ______.

The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E. The electric field intensity produced by the radiations coming from 50 W bulb at the same distance is ______.

The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is ______.

Why does microwave oven heats up a food item containing water molecules most efficiently?

The magnetic field of a beam emerging from a filter facing a floodlight is given by B₀ = 12 × 10^–8 sin (1.20 × 10⁷z – 3.60 × 10¹⁵t) T. What is the average intensity of the beam?

Electromagnetic waves with wavelength

1. λ₁ is used in satellite communication.
2. λ₂ is used to kill germs in water purifies.
3. λ₃ is used to detect leakage of oil in underground pipelines.
4. λ₄ is used to improve visibility in runways during fog and mist conditions.

1. Identify and name the part of electromagnetic spectrum to which these radiations belong.
2. Arrange these wavelengths in ascending order of their magnitude.
3. Write one more application of each.

What happens to the intensity of light from a bulb if the distance from the bulb is doubled? As a laser beam travels across the length of a room, its intensity essentially remains constant. What geometrical characteristic of LASER beam is responsible for the constant intensity which is missing in the case of light from the bulb?

Figure shows a standard two slit arrangement with slits S₁, S₂, P₁, P₂ are the two minima points on either side of P (Figure). At P₂ on the screen, there is a hole and behind P₂ is a second 2-slit arrangement with slits S₃, S₄ and a second screen behind them.

For light diverging from a point source ______.

1. the wavefront is spherical.
2. the intensity decreases in proportion to the distance squared.
3. the wavefront is parabolic.
4. the intensity at the wavefront does not depend on the distance.

Is Huygen’s principle valid for longitudinal sound waves?

Consider a point at the focal point of a convergent lens. Another convergent lens of short focal length is placed on the other side. What is the nature of the wavefronts emerging from the final image?

What is the shape of the wavefront on earth for sunlight?

Consider Figure for photoemission.

How would you reconcile with momentum conservation? Note light (photons) have momentum in a different direction than the emitted electrons.

O₂ molecule consists of two oxygen atoms. In the molecule, nuclear force between the nuclei of the two atoms ______.

Would the Bohr formula for the H-atom remain unchanged if proton had a charge (+4/3)e and electron a charge (−3/4)e, where e = 1.6 × 10^–19C. Give reasons for your answer.