List of practice Questions

Define coherent sources. Can two independent sodium lamps be coherent?

A beam of light consisting of a known wavelength 520 nm and an unknown wavelength λ, used in Young’s double-slit experiment, produces two interference patterns such that the fourth bright fringe of unknown wavelength coincides with the fifth bright fringe of known wavelength. Find the value of λ.

(a) "EM wavelength correlates with the size of the radiating system." Give two examples.
(i) Why do long-distance radio broadcasts use shortwave bands?
(ii) Why are X-ray telescopes satellite-based, while optical/radio telescopes are ground-based?

(i) Derive the impedance of an R-C series circuit connected to an AC source v = v_m sin(ωt).
(ii) When does an inductor act as a conductor? Explain.
(iii) A lamp (R) and inductor (L) in series with 220V-50Hz AC give 11A. With 110V DC, it gives 11A. Find L.

Coils P and Q. Current in P induces current in Q. (a) Explain the phenomenon. (b) Two factors affecting current in Q. (c) Direction of current in Q when current is in P and (i) R increases, (ii) R decreases.

(a) Two characteristic properties of nuclear force. (b) Plot potential energy of a nucleon pair vs. separation. Two conclusions from the plot.

A transformer has 500 primary turns and 5000 secondary turns. Input is 220V-50Hz. What's the output?

Who first produced and observed EM waves in the 25mm-5mm range?

Differentiate between diffusion and drift current. Explain their role in p-n junction formation.

An air-filled parallel plate capacitor (d = 1mm, C = 20pF) is charged to 4.0µC. Find work done to increase plate separation to 5mm (constant charge).

(a) State Bohr's postulates for the hydrogen atom.
(b) A hydrogen atom de-excites from level n to (n-1). Show that emitted frequency ν ∝ α/n³ for large n (α = constant).

Two batteries (6V, 0.8Ω and 3V, 0.2Ω) are connected in series with external resistance R. Find R so that the potential difference across the 6V battery is zero.

An object is placed 30 cm in front of a concave mirror (radius of curvature 40 cm). Find: (i) image position (ii) magnification

How does conductivity of an intrinsic semiconductor vary with temperature? Show in a plot.

Charges Q1, Q2, and Q3 are at (-d,0), (0,0), and (d,0). Q1=Q3, Q2>0. Find the nature and value of Q1 for zero potential energy.

A bar magnet (2.5 J/T) is aligned with a 0.32 T field. (a) Find work done to align it (i) normal, (ii) opposite to the field. (b) Find torque in both cases.

Four cells (emf E, internal resistance r) are connected in series, but one is wrongly connected. Find the equivalent emf and internal resistance.

A wire bent into circular loop A carries current I. The same wire is bent into loop B with two turns, same current. Find the ratio of magnetic fields at the centers of A to B.

A conducting circular loop (radius shrinking at 1 mm/s) is in a uniform magnetic field B = 50 mT, plane perpendicular to the field. Find the induced emf when the radius is 4 cm.

Electric and magnetic fields of EM waves are:

Two beams (3.3 eV and 11.3 eV) illuminate a metal (work function 2.3 eV). Find the ratio of maximum electron speeds.

An electron and a proton have the same wavelength λ. This implies they have the same:

A charged sphere (radius r, surface charge density σ) has electric field E. If the radius doubles (charge density constant), what's the ratio of the old to new electric field?

State any two properties of a nucleus.